First post :-) Long time user. WinSCP is the best, I just want to say thanks for bringing us all such an amazing app & appreciate the hard work you have put into this (I donate most years & encourage everyone to donate too if they can).
As I've gotten older my eyes have gone & I wear readers. I have trouble hitting the tiny arrows on the drop down icons (eg bookmarks & filters) I have tried adjusting the display scaling on W10 and yes everything gets bigger except the icons plus this steals screen real estate (not an easy choice on a laptop) And display scaling is a drastic step when you just need slightly bigger icons.
When I create desktop apps I use 'ico' icons files which have many sizes included (16,32,48 etc...) & give the user the choice on which one to choose (in WPF apps that is), not trying to teach you to suck eggs but this approach puts the user in charge at the app level so we don't have to bother with system wide settings.
After reading a few posts on the icon sizing scaling, can I ask if you are planning on bringing in the scaling icons you have mentioned, I understand the cost of a new set of icons was prohibitive. If you were to set up a fund page for this I would happily donate & im certain many users would happily donate too.