Right-click include/exclude not working right

In the "Source" pane of the "Sync" tab, the user can right-click on a file or folder and get a context-menu prompt that offers to include or exclude the selected folder/file to the currently selected "Rules" set.

This would be very handy if it worked properly but unfortunately it's rather squirrelly.

I started out with three rules in my "Rules" set, and when I attempt to add more "Exclude" rules to it via the right-click menu, instead of adding the new rules onto the end of the ruleset, it just semi-randomly replaces one of the existing three rules.

Not only does this disrupt my existing rules, but it makes it impossible to add multiple files/folders to the Exclude list -- when I try to do that they don't accumulate, they just replace each other.