I've always used SourceTree for my GIT interactions, but recently decided to try staying within Xcode for everything. However, I can't find everything. For instance, while I see branches, tags and remotes, I don't see stashes. Are they there?
Xcode 9 does not have support for stashes.
Xcode 11 Update
Xcode 11 adds support for Git stashes. Choose Source Control > Stash Changes to stash changes. You can view your stashes from Xcode's source control navigator. The stashes are in the Stashed Changes folder.