If a folder has items that aren't sorted alphabetically (or in any other fashion desired by the user), currently there are three options:
- Sort it automatically the way they want but be forced to change the sort method from 'Custom' which will cause other folders that are custom sorted to be out of order
- Leave it unsorted
- Manually sort it alphabetically
I propose adding an option to set the current sort order as custom. This way the user could sort alphabetically (or whatever method they want) automatically, then click 'Set current sort order as Custom' and then switch back to 'Custom' sort order (or perhaps that could even be done automatically).