From version 1.2.1, we already added the possibility to unequip skills.
Try updating the game. If you still can't unequip it, please let us know and we'll manually do it from our game database.
UPDATE
Even though we can't seem to reproduce your issue (equipping a scroll), we still tweaked the inventory system in order to force display the unequip button. You'll find this new feature on v1.2.3 (available tomorrow on Google Play).
Yes, thanks. Now, there's a different kind of issue, though. The icon disappears from the slot but trying to equip a skill in slot 2, as shown in the pic, results in still having buttons related to scrolls
I'm not sure I understand how to replicate your issues.
I just unequipped slot 2, then I'm trying to equip a skill into it, and I can't seem to find any issues with it. Perhaps am I missing anything? Any help in reproducing the issue would be greatly appreciated, thanks