Perfect.

Would be nice if one could configure the addon.
E.g.: I would like that:

new tabs
tabs opend from outside of firefox
tabs opend from pinned tabs

would indeed open on the right.

But for:
tabs opend from other tabs
I would prefer the current behavior: opening next to the parent tab.

Would be nice if one could select which behaviors one want's enabled

Thank God, I finally found the simple cure to have new tabs open consistently to the far right and not interfere with the order of open tabs. Thank You!