@proparxsa Go to the addons.opera.com website, sign in with the same login you use here, then click on Develop. Mind you, judging by reports here the moderation process (for approval of your extension) can be somewhat slow.
I want to give an update. After multiple tries of checking and unchecking the checkboxes, at some point it seems I succeeded in selecting the one I wished to and I also managed to deselect the other at the same time.
Saving the choices for these checkboxes seems to work arbitrarily.