The ability Quoratum's Guard says that it can be binded to a quick slot, however the skill refuses to move when dragged with the mouse. This is a problem as the skill requires a Quick Slot to use.

Hi there, I assume you are Awakening Nova. In awakening, the skill "Combust Life" replaces "Quoratum's Guard", which is why the latter skill cannot be used individually. The same happens when you e.g. try to drag "Countergambit III" while having "Absolute: Countergambit" unlocked. If the skill description mentions the preceding skill, only the higher tier version can be used.