4Lakes

I have not tried every tool with every setting, but the following occurs in both Affinity Photo Windows 1.6.5.123 and the beta 1.7.0.258:
Some tools that re-set to default values include:
Color Picker Radius if changed from 1x1 will reset to 1x1 if the same file is saved & then re-opened or if a new file is opened. Similarly, Flood Select Tool Tolerance if changed from 20% will re-set to 20% if the same file is saved & then re-opened or if a new file is opened. Patch Tool Rotation and Scale if changed from rotation 0 degrees and scale 100% will reset if the same file is saved & then re-opened or if a new file is opened. Conversely, some tools that hold their values after closing & reopening the same or a different file include:
Selection Brush Width if changed from default retains the changed value if the same file is saved & then re-opened or if a new file is opened. Burn Brush Tool: Width, Opacity , Flow, Hardness, Length retain changed values if the same file saved & then re-opened or if a new file is opened. I did not test if Stabilizer, Mirror, Lock, Tonal Range, Protect hue retain their status or not. Non-systematic testing of other tools indicates that some re-set to a default value while others retain a changed value.
If desired, I can send the rather tedious step-by-step testing that shows the above behavior.
I am no expert in Affinity Photo or interface design, but some consistency would be helpful. The ability to set tool behavior (retain vs reset to default when a file opens) either for all tools, by tool groups, or by individual tools would be helpful. An atomistic tool-setting-by-tool setting would be excessive (e.g. a user could set Burn Brush Width and Flow to reset to defaults but Burn Brush Hardness and Length would not reset).
It might be desirable for the user to be able set the default values. For example, if you routinely worked with high resolution images, possibly higher default values for some tools would be more convenient.
For comparison, in Adobe Photoshop CC the Color Picker radius or Magic Wand radius (which are always in agreement, changing one changes the other to the same value) will stay at the value when changed, they do not reset to a default when the file is closed or a new file is opened. This is different from Affinity Photo's re-setting the Color Picker Tool to 1x1. Similarly, the Ps Patch Tool retains the Structure and Color setting when these are changed.
 

I do not have or use Designer, but in Affinity Photo Beta 1.7.209 the Dirk Wustenhagen Fine Art Texture Collection brushes seem to work as texture.
Machine: Windows 7 Professional 64-bit up-to-date per Windows Update, Service Pack 1, Processor: Intel Core i7-3770 CPU @ 3.40GHz, 32.0 GB RAM, Windows Experience Index 7.7 (on a scale of 1.0 to 7.9), Graphics card: GeForce GTX 970 version 385.69
Since there are numerous options for the Brush settings, I am including screen captures of the General, Dynamics, Texture, and Sub-Brush panels as well. I presently rarely use brushes, so these are almost always the default settings in the panels. Perhaps different settings of these panels causes a problem?

Please allow the user to manually choose the manufacturer and lens model as Adobe does in Adobe Camera Raw. This lets the photographer select the correct lens in the lens correction database when the photographer uses a completely manual lens for which the RAW file will not have the data for manufacturer, lens model, f/stop etc. Similarly, when using electronic lens adapters such as the Metabones adapter for Canon EOS lenses on Sony alpha series mirrorless cameras bodies (e.g. a7r2), the Raw file EXIF data has the wrong manufacture and lens model because the electronic adapter must make the Canon lens appear to be a Sony lens model of the same focal length and f/stop.
For example, if the widely used Canon 24-70mm f/2.8 L II USM is attached via a Metabones adapter to a Sony a7r2 body, the EXIF data records the lens as a Sony "24-70mm F2.8 G SSM II". The other EXIF data for focal length the zoom was at and exposure f/stop are correct. In Adobe Camera Raw's lens corrections, I can simply select the Lens Profile Correction for the "Canon EOS 24-70mm f/2.8 L II USM" and have the proper lens corrections applied. Similarly, if I use a Rokinon 14mm f/2.8 completely manual, no electronics, lens on a Sony a7r2 body, I can select that Lens Profile Correction in Adobe Camera Raw despite the lack of any EXIF lens data in the Raw file.
At present, the only way to have Affinity Photo Develop apply the correct LensFun database corrections is to use ExifTool and change the data in the Raw file before Affinity opens the file. This is both time-consuming and I would rather not tamper with a proprietary Raw file format.
Thank you.

I too think the user should be able to choose if lens corrections on an image should be automatic, based on EXIF data, or instead be specified by the user.
Mirrorless cameras such as the Sony a7 series cameras are a case in point. There are several electronic adapters that allow non-Sony lenses to use many of the camera's electronic functions. One way this is done (e.g. Metabones adapter) is the adapter identifies the lens in use as an equivalent Sony lens. For example, when a Canon EF 24-70mm f/2.8L II USM is attached via the Metabones adapter, the RAW file EXIF data records the lens as Sony's "24-70mm F2.8 G SSM II". Rather than go through the process of changing data in the proprietary RAW file with the risks of corrupting the file, the user should be able to select the correct lens profile.
The short flange to sensor distance in mirrorless cameras also allows use of numerous purely mechanical lenses, some "vintage", some new. For such lenses there is no EXIF data recorded. Once again, the user should be empowered to be able to select the correct lens profile and not be forced to undertake the risk of editing a proprietary RAW file format.
Finally, competing RAW processing software allows users to select the correct lens profile. Adobe Carmera RAW allows this. Adobe Lightroom allows this. Capture One allows it (if a profile is available). ON1 Photo RAW 2018 allows it. Affinity Photo needs to keep up with the competition.
I made a similar request feature request here some time ago LINK.

I too think the user should be able to choose if lens corrections on an image should be automatic, based on EXIF data, or instead be specified by the user.
Mirrorless cameras such as the Sony a7 series cameras are a case in point. There are several electronic adapters that allow non-Sony lenses to use many of the camera's electronic functions. One way this is done (e.g. Metabones adapter) is the adapter identifies the lens in use as an equivalent Sony lens. For example, when a Canon EF 24-70mm f/2.8L II USM is attached via the Metabones adapter, the RAW file EXIF data records the lens as Sony's "24-70mm F2.8 G SSM II". Rather than go through the process of changing data in the proprietary RAW file with the risks of corrupting the file, the user should be able to select the correct lens profile.
The short flange to sensor distance in mirrorless cameras also allows use of numerous purely mechanical lenses, some "vintage", some new. For such lenses there is no EXIF data recorded. Once again, the user should be empowered to be able to select the correct lens profile and not be forced to undertake the risk of editing a proprietary RAW file format.
Finally, competing RAW processing software allows users to select the correct lens profile. Adobe Carmera RAW allows this. Adobe Lightroom allows this. Capture One allows it (if a profile is available). ON1 Photo RAW 2018 allows it. Affinity Photo needs to keep up with the competition.
I made a similar request feature request here some time ago LINK.

I too think the user should be able to choose if lens corrections on an image should be automatic, based on EXIF data, or instead be specified by the user.
Mirrorless cameras such as the Sony a7 series cameras are a case in point. There are several electronic adapters that allow non-Sony lenses to use many of the camera's electronic functions. One way this is done (e.g. Metabones adapter) is the adapter identifies the lens in use as an equivalent Sony lens. For example, when a Canon EF 24-70mm f/2.8L II USM is attached via the Metabones adapter, the RAW file EXIF data records the lens as Sony's "24-70mm F2.8 G SSM II". Rather than go through the process of changing data in the proprietary RAW file with the risks of corrupting the file, the user should be able to select the correct lens profile.
The short flange to sensor distance in mirrorless cameras also allows use of numerous purely mechanical lenses, some "vintage", some new. For such lenses there is no EXIF data recorded. Once again, the user should be empowered to be able to select the correct lens profile and not be forced to undertake the risk of editing a proprietary RAW file format.
Finally, competing RAW processing software allows users to select the correct lens profile. Adobe Carmera RAW allows this. Adobe Lightroom allows this. Capture One allows it (if a profile is available). ON1 Photo RAW 2018 allows it. Affinity Photo needs to keep up with the competition.
I made a similar request feature request here some time ago LINK.

Please allow the user to manually choose the manufacturer and lens model as Adobe does in Adobe Camera Raw. This lets the photographer select the correct lens in the lens correction database when the photographer uses a completely manual lens for which the RAW file will not have the data for manufacturer, lens model, f/stop etc. Similarly, when using electronic lens adapters such as the Metabones adapter for Canon EOS lenses on Sony alpha series mirrorless cameras bodies (e.g. a7r2), the Raw file EXIF data has the wrong manufacture and lens model because the electronic adapter must make the Canon lens appear to be a Sony lens model of the same focal length and f/stop.
For example, if the widely used Canon 24-70mm f/2.8 L II USM is attached via a Metabones adapter to a Sony a7r2 body, the EXIF data records the lens as a Sony "24-70mm F2.8 G SSM II". The other EXIF data for focal length the zoom was at and exposure f/stop are correct. In Adobe Camera Raw's lens corrections, I can simply select the Lens Profile Correction for the "Canon EOS 24-70mm f/2.8 L II USM" and have the proper lens corrections applied. Similarly, if I use a Rokinon 14mm f/2.8 completely manual, no electronics, lens on a Sony a7r2 body, I can select that Lens Profile Correction in Adobe Camera Raw despite the lack of any EXIF lens data in the Raw file.
At present, the only way to have Affinity Photo Develop apply the correct LensFun database corrections is to use ExifTool and change the data in the Raw file before Affinity opens the file. This is both time-consuming and I would rather not tamper with a proprietary Raw file format.
Thank you.