Your comments

Your documentation for subtrees (https://docs.syntevo.com/SmartGit/Latest/Subtrees.html) does not mention Pull to update the subtree from its remote, nor could I find anything in the UI.  I ended up doing directly with Git:

git subtree pull --prefix <local folder> <remote repository> <branch>

This seems like a pretty fundamental operation and it would be nice to be able to do it from SmartGit.