I would like to create a way for players to use Abilities/Spells while performing some control combo with the Rightclick and Leftclick. An example would be, To trigger Ability [X] use the right and left control of your mouse and perform the combo [Right+Left+Right].
This might be possible with PlayerInteractEvent. Store the action sequence that they do (and probably some timing information too) and see if it links to a set action sequence that you pre-program. Then cast the spell.
If all spells are triggered by mouse buttons (no keys are involved), then I'm also pretty sure that this can be done with PlayerInteractEvent. @Zaltuğ Kırcı You have to say which Minecraft version you want your plugin to be. EDIT: ...and you should probably go a little more into detail on what kind of spells and abilities you picture.
I believe crouching may also work, though it would be hard to link it mixed in with mouse events. Unless I'm dumb; also possible.