Commit dialog always selects all files even if openend on a single file
When a user right-clicks on a single file to perform a commit, the window is populated with all the changed files and the check boxes are all selected.
The default action for a single file selection should be that only that file has its checkbox selected.
Otherwise the user must select None, and then select the intended file.
To upload designs, you'll need to enable LFS and have admin enable hashed storage. More information