This program is amazingly unintuitive. It's one of the main reasons I feel like I can't just jump ship from Photoshop or Illustrator to Photo or Designer.
For example, simple things like filling a selection should be reasonably intuitive. I realize it's hard to target everyone's train of thought, but here's mine:
1) Open an image in Designer
2) Make a selection of what you want to fill
3) Use the 'Fill Tool' and draw in a fill within that selection based on whatever 'Fill Tool' options I've chosen.
However, all that happens is that I get a line that looks like Photo's 'Gradient Tool,' but nothing happens. I go to Tutorials under the Help Menu, which takes me to a website, where I do a search for Fill Tool and I'm greeted with a myriad of things that don't apply. So, I go to Help... under the Help Menu and look up Fill Tool and I'm greeted with the list of information below (which is neither descriptive enough to be useful, nor simple enough in application to be effective).
Considering the first two part of this list of information, where the fill tool allows you to adjust the fill, then I expect to be able to adjust from no fill to a fill and to apply the flood with a single click, but that never happens.
Taking this a step further, if I have a selection made and try to paint with the vector brush inside that selection, the paint doesn't obey the boundaries of the selection. What's the point of the selection if it doesn't set boundaries?
Search results for fill tool
The Fill Tool allows you to adjust the fill and line colors applied to vector and text objects.
The Flood Fill tool allows you to fill in areas of your page, selection, or object with a single click.
There are various ways to select and apply color in Affinity apps.
The Swatches panel stores a selection of color, gradient and recently used document color swatches for applying to objects.
Customize gradients for object fills and lines.
A list of commonly used shortcuts.
The Color panel is used to apply color to objects.
About Lines and Shapes
Open curves and closed shapes can be created and are controlled by nodes and control handles.
Artboard color and opacity
Discussion of artboard color properties.
The Transparency Tool allows you to apply and edit transparency gradients to vector and text objects.
The Outer Shadow effect is used to add a shadow to edges.
Find out about transparency and how it is applied to your design.
The Pen tool is used to draw very precise curves and shapes.
The Pencil Tool allows you to create hand-drawn lines and shapes.
Pick up colors from objects on your page or pixels on your screen.
The Transparency Editor dialog lets you customize transparency gradients for object fills and strokes.
The Move Tool allows you to select, move, rotate, and resize objects.
Layer masks allow you to selectively hide layer contents to reveal layers below the masked layer.
The Ellipse Tool takes the hassle out of creating circles and ellipses.
The Corner tool rounds sharp corners on closed shapes.
The Inner Shadow effect is used to add a diffused shadow to the inside of an object.
An overview of Affinity Designer key features.
Color Picker Tool
The Color Picker Tool samples colors from anywhere on your document or screen.
Use frame text for paragraphs with a formalized structure and layout.