It seems to me that there are only so many possible actions and combinations of actions that can be done on a skateboard, especially on flat ground, and the way that your body moves while performing a trick is generally - from what I understand - not the basis for a "new" trick. For instance, there are only two forms of the ollie: itself and the nollie. There are only so many yaw rotations that can be done on a skateboard that are considered (pardon me, here) tricky. For instance, 180°, 360°, 540°, 720°, 900°, 1080°, etc. (A 90° spin might exist, but would be difficult to pull off while moving, and at some point the board has a limitation to how much it can spin on the yaw axis, especially on the ground, before it cannot be spun any more due to the limitations of gravity.) Likewise, there are only so many rolls and pitch rotations that can be done.
Given this, have all skateboard tricks already been invented? Furthermore, have all skateboard tricks already been named? I suppose it is hard to quantify something that has yet to be invented because it, by definition, does not exist yet, but I also have yet to discover a definitive list of all skateboard tricks that either can be done or have been invented/named.