I normally keep certain skills on specific hotkeys (eg. WW3 is always in slot 1 (hotkey ‘q’) and diso3 is always in slot 5 (hotkey ‘f’)). It can be a frustrating experience when hunting in deep UW and I lose my skill in slot 5. I always bring my books with me, and quickly relearning the skill while in combat isn’t too bad. Although quickly typing:
If multiple slots are empty, they could be populated in order. For example, consider the scenario that you have 4 skill slots available and currently have WW in slot 1 and dash in slot 2, with two empty slots (3 and 4). When you learn shell for the first time, it would fill slot 3.
If all slots are full, the new ability learned could simply replace the skill in slot 1 or in the last slot available depending on how many ability slots the player has unlocked, without shifting everything around. This could also help with grinding research.
Additionally, I would like to see a hotkey added for skill slot #6. Customizable hotkeys would also be a very nice quality of life improvement.