+1000 also...
I often work on several projects in parallel, or complex projects (in terms of file organization). So, several Affinity documents to export, each in a different folder...
It would be nice to distinguish (as paristo said) :
Save As = Open Affinity Document Folder
Export Slices = an export folder, specific to the current document - and memorized from one time to the next
Option: to be able to choose that some slices are in specific folders (ex: pdf in one file, png in another, HighDef in one, LowDef in another ...
This is probably the most frustrating feature of Affinity (maybe the only one ...) I hope...