First: Affinit Designer is really great - thanks to the Affinity team! (Former-time Corel user, then Inkscape, now switched to Affinity due to CMYK and better color management)
My request:
I often use Save-As to generate numbered versions of files (as backups, and so that when I discuss them with a client, we can refer to which version we are talking about). In the Save As dialog, it appears that AD defaults to the folder where I last saved anything. This is very tricky when working on file