I asked the developer and he answered very fast with some guidelines and explanations on my case.
I just have one suggestion: Is there a way to force a group tab? If you are in a Gmail tab and open many links, a "Gmail tab" parent tab appears and all those opened links go as childs into that opening link.
Is there a way to select many tabs and turn them into childs of a parent tab, too which we can give a name?
Even, is there a way to pin a parent group?
I do not know if this is at all possible but thanks for a wonderful extension.
PD: I have read that Firefox 64 will have a better "tab" control. Will this improve the experience with TST?