The regular system for Middle Rings in Yoshi's Island sucks.
It's overly complicated, rather limiting, and even pretty wasteful.
It is very irritating to edit middle rings when making a hack, even with the midring editor. The editor itself is nice, but the system is hard to figure out in general, making the editing process tough.
This patch solves that problem by simplifying things:
Each sublevel in the game now simply has X, Y coordinates you can specify - these coordinates will act as the return coordinates after retrying for the Middle Ring.
No more weird pointers, no more item page header to worry about, just a table of coordinates that line up with sublevel.
"better_midrings_data.asm" is the file you'll be interested in; the sublevels are listed on the right in comments, and the data is just X, Y (tile coordinates straight from Golden Egg). The data I've supplied is copied straight from vanilla, so the game should work exactly the same. Editing this file for your hack will simply work after patching!
"better_midrings.asm" file contains the code necessary to make this work, and already includes the other file.
Use a Yoshi's Island U1.0 ROM, and patch with asar:
asar better_midrings.asm myrom.sfc
Asar 1.37 is preferred but older versions should work fine.
Notice any differences, bugs, or quirks? Send me a PM or hit me up on the SMW Central discord.
A bit of an issue with this patch as it currently exists: it completely removes the "Entrance type" option from the middle ring data. Normally this is fairly easy to work around, but it means you can't have a middle ring in a skiing section restart you on skis, for example.
If there's anyone able to create an alternate version of this patch which includes entrance types, please post in the #misc-hacking channel on the SMWC Discord.