Hi!
Long time player, first time really delving into mods and things, discovering the ease with which modding can be done.
I have an odd suggestion, one I can't find any other discussion of in searching.
I don't know exactly how Menus and Submenus work in the hard code of the game. Many are hardcoded due to workarounds and requirements of new systems, such as the new arrow creation system. This has, it seems, for many years, caused endless headaches for modders. From an external, modding-only perspective, it looks like Menus are created in menudef_[YourModHere].txt files, and a single layer of Submenus are then defineable in their respective diy/biy text files.
My suggestion is about creating nested submenus. This would likely solve many organisational issues with the otherwise limited menu space.
A nested submenu would simply be some kind of entry into an existing submenu document that isn't a recipe, but instead another submenu. Whether in another text file, or nested in the same file as the ur-menu, submenus would allow for much more organised and less cluttered submenus, especially given the slow increase in content over time in the base game, as well as the nightmarish amounts of menu entries in mods like BAC (spirits protect you if you want to use BAC and some other mods, too!)
Changing the number of displayable menu entries is, I would guess, easier said than done, which would be why it hasn't been done.
Hence, the suggestion: nested submenus.
Even just the ability to nest a single new set of submenus within the existing submenu layer would increase the number of total menu options available to the base game and modders alike, by 25x, or over 15000 new menu entries available to everyone.
Thank you for reading my suggestion. I hope, if nothing else, it inspires some improvement in this wonderful experience of a game.