I just recently discovered that you can select and drag multiple Safari tabs by holding shift or command, just as you would to select and drag multiple items in Finder.
I’m sure it has been added recently or was hidden in the system for like 15 years.
Sadly it’s Safari only, so it doesn’t work on other system tabs like Finder or iA Writer.
My use case is to select those tabs I want to save as a group, right click one of those tabs to add them all to a new Tab Group (to keep things neat and tidy).