When right-clicking a tree tab with children, actions for bookmarking, (copying,) duplicating, and moving should also be provided in a section which would apply to child tabs as well.
This would end up with a fairly long list, but in my opinion it's worth the tradeoff. Here is what I might suggest:
Bookmark Tab
Copy Tab Link
Duplicate Tab
Move Tab ›
Bookmark Tree
Copy Tree Links
Duplicate Tree
Move Tree ›
Close Tree
Pin Tab
Reload Tab
Close Tab
Close Tabs Below
Close Other Tabs