how to unsynch scrinver file with external document ?

how do i unsynch a my scrinver file with a external document ?

Are you using the External Folder Sync feature?

In that case, just go to File > Sync > With External Folder and untick the first box ‘Sync files in this project with external folder’. The ‘Sync’ button will change to Save - press that and the project won’t sync again (until you tick the first box again, of course.)