Yes, I have, but staging a complete directory, e.g., the src directory, is quite easy by doing a git add src. If there were a possibility to move files from modified to staged from Browse Repository or from Compare Workspace with git, I would use it more I think. I'm not super much into git, but my workflow involves the following. I guess one can do all these steps with slickedit.
git status - to see which files have been modified
git diff or git diff --cached - to see changes made to modified or staged files
git add - to stage files before commit
git commit - to commit staged files
git push - to send local commits to git server
git branch - to create a new branch
git checkout - to change to another branch
sometimes I also do
git stash and git stash apply
