I found a workaround.. for saving Tab Group links:
Open up Tab Groups in the Sidebar on the Left
Control-Click or Right-Click on the name of the Group
Select Copy Links
Paste the links into a Text Only (not Rich Text) document [Save]
What you will see is something like this:
SAMPLE TAB GROUP
Apple
https://www.apple.com/
iPhone - Apple
https://www.apple.com/iphone/
You won’t be able to restore the Tab Groups if something goes wrong and your groups are lost, but you will have the links. At least if you have a valuable link you can’t afford to lose, you can copy/paste the link to re-visit the page