This huge wall of text will be attempting to explain a method to despawn the plant jump in 8-2, for Super Mario Bros. Speedruns.

There will be a few requirements that needs to be met, and getting even one of those requirements met is very unlikely. As a result, if my logic has no flaws, a lua script must be written to find a framerule where all of these requirements are met.

The game can have no more than 6 sprites/enemies on the screen at a time. To despawn the plant jump plant, 6 enemies already have to be on the screen. The plant before the plant jump and the koopa before the plant jump count as sprites, so that's two sprites already. The plant before the plant before the plant jump is too far away to count as a sprite to despawn the plant jump plant (according to blazit). And also according to blazit, if too many bullets are on the screen, the plant before the plant jump will despawn, which will make the plant jump plant not despawn. So, we need to find a way around this.
The two beetles before the plant before the plant before the plant jump as well as the plant before the plant before the plant jump will count as sprites towards despawning the plant before the plant jump as well as the koopa before the plant jump. These two sprites must not be despawned. So, we must despawn those two beetles and the plant before the plant before the plant jump.
To despawn the two beetles, there must be 6 sprites on the screen. The beetle before those two beetles counts as a sprite, so we need 5 more sprites on the screen. This is the first requirement - 5 bullets must be on the screen before those two beetles, so that those two beetles are despawned.
Next, the plant before the plant before the plant jump must be despawned. Since the two beetles are already despawned, we need 6 bullets on the screen - that is the second requirement, 6 bullets must be on the screen when despawning the plant before the plant before the plant jump.
After this, exactly 2 bullets must go off the screen so as to not despawn the koopa and plant before plant jump (Third requirement). And by the time we reach the plant jump plant, 4 bullets, the koopa, and the plant before the plant jump should be on the screen if all goes well.
The fourth requirement is an optimal bullet shot for BBG.
If all these requirements are met, another framerule should be able to be saved. However, there are many many framerules to be checked before a framerule with these requirements are met. A lua script should be written to check a bunch of possible framerules. The thing is, I'm stupid and don't know a thing about lua scripts. Can someone pls help - zsjetu9