I'm surprised that this ability is locked away from players, I would really love if it was possible to key-bind hotbar actions to the mouse's scroll wheel. The scroll wheel is literally one of the most easily accessible "keys" a player on the PC has access too, forcing players to keep it bound to the camera is, in my opinion, rather restricting and limiting.

In other games I bind all of my pet actions to the mouse wheel using it to send off my pet, call back my pet, tell my pet to move to a specific location, have my pet use a specific ability, and so forth (scroll up, scroll down, alt scroll up/down, shift scroll up/down, et cetera). Which for me provides a very tight and precise feeling of control over the pet (flick the mouse wheel to send it to attack, roll it to call the pet back).

I hope that you might consider providing PC players the ability to utilize the mouse wheel for keybindings at some point, thank you very much.