The current Document Picker is seriously crippled. Heck, it can't even choose the sort order, make list view as default, and really manage your files! Moreover, for some reasons Apple has not yet implemented a way to remove unused app containers, and makes the Picker being flooded with a sea of garbage.
But at least its Date view does sort in descending order by default. So making use of this property, you may tag the app containers you wanna keep on top of all on your Mac. This makes the app container to be modified, has their date modified changed and eventually push them to the top of the Document Picker.
Unfortunately, this trick does not work on custom folders, as they are always listed after the app containers in the Date view... What a weird design choice.
But at least its Date view does sort in descending order by default. So making use of this property, you may tag the app containers you wanna keep on top of all on your Mac. This makes the app container to be modified, has their date modified changed and eventually push them to the top of the Document Picker.
Unfortunately, this trick does not work on custom folders, as they are always listed after the app containers in the Date view... What a weird design choice.