And I really mean move, not copy.
The difference between copy and move is that copy... copies, but move dies copy->verify->delete original, in a single operation of the user.
Preferably, that is reliable.
Meaning it checks the bookmarks have been successfully created before closing the related tab.
Also it should be clear what bookmark folder it is going to put the tabs in.
Because the current bookmark manager, it is easy to end up dumping all your tabs in the parent folder of tge destination you indented.
Or end up creating an extra child folder inside your intended destination bookmark folder
Would also be nice to have quality of life features, such as a default bookmark folder.
The option to put the bookmarks in a folder named with today's date.
Maybe an option to specify a default destination bookmarks folder on a per site domain basis
https://addons.mozilla.org/en-US/firefox/addon/tabs-aside/ looks like could be a candidate for you. But I don't know if it closes the tabs automatically after creating bookmarks. From the terminology "aside" I would assume its "move" operation. I never used this program and cannot say how trustworthy or good it is and only post it here based on the description.
"They will be stored in a new folder in your bookmarks and can be restored all at once via the sidebar."
This might be it ! Thanks !