This block is the vine. When it is caught in the vine, player moves in each direction.
Changelog: 2019/08/09 v1.0 - submit.
The blocks work fine besides a minor issue and a major one:
Minor: the horizontal conveyors don't push Mario if he stays on the very edge of the vine.
Major: if you have an upwards conveyor with a solid block above, Mario will be pushed inside it and clip through it. If there's a wall on the left side, Mario will die as a result of this.
This can be fixed by adding a check for Mario's blocked status in MarioAbove, and if he's blocked then increasing $96 will prevent him clipping (or you can STZ $74 to make him fall off the vine).
If you fix this, you could also consider adding the frames to skip as a define, so that the user could easily customize the speed of the conveyors. Also, the block descriptions have a grammatical error.