This code allows you to create a level with multiple paths, where the correct path must be chosen to progress, similar to 4-4 and 7-4 from SMB. You can define several rectangles, and then if Yoshi reaches a particular x-position without entering any of these rectangles all horizontal entrances towards right (sprite 0D0) will despawn. For instance, this can be used to despawn an entrance that sends you back to the start, if you have chosen the correct path, thus allowing you to continue.
;This has a list of all coordinates of the rectangles where this will trigger.
!length = #$07 ;Replace with actual length of tables, in bytes
Uh, you utilize label maths to avoid having the user manually entering the length of tables:
Replaced a single instance of $7F0000 in the code with !flag (apperantelly, you forgot this one).
It works... but it could have been more user friendly. For example, I'd specify each box for the wrong path on a single line. I'd also make use of Asar maths so you don't have to specify the entries. You also could have made it so to disable sprite 147 (horizontal entrance to the left).
I also see ways of improvement. One example I can think of is the constant switching between 16-bit and 8-bit mode. I can understand it if you set the flag that the wrong path has been taken but if you compare it, you can just clear the high byte with AND #$00FF. Another example is that you don't use the SRAM mirrors $6000-$7FFF beyond the use of the sprite table $7360,x.
Nonetheless, it is a way to disable horizontal warps depending on Yoshi / the player's path so accepted.