Ability to deactivate sync for a file or folder

### Is your feature request related to a problem? Please describe.
Once I started synchronizing a file or a folder, I can't deacivate the synchronisation for this file or folder. I have to delete it localy on my phone. So it's impossible to just download a file or folder once.

### Describe the solution you'd like
I want the ability to deactivate the synchronisation for a file or folder.

### Describe alternatives you've considered
Synchronizing the file or folder, copy it to another location on the phone an deleting the synchronized file or folder. This is annoying.