An option would be good to enable customization of the ungroup feature as well.
I mean it is good, that I am able to group windows together with only mouse drag, but it is bad, that I can ungroup windows accidentally in the same way, by just dragging a window.
Because in lots of cases I use to 'drag' windows, so as to change position, and now I accidentally ungroup the tabs.

So It would be nice, to give the option to set up the ungroup feature, so I could use mouse to group, but shift+mouse to ungroup the tabbed windows, or I could disable ungrouping with mouse at all.