KrimtonZ has gotten us all an early Christmas present - the official release of the Majora's Mask practice ROM! kz is the Majora's Mask equivalent of gz, and has many of the same features you may be familiar with, including, but not limited to:

-input viewer
-command menu
-debug menu
-warps
-inventory management
-cheats
-equip manager
-memory viewer/manager, watches
-saving and loading memfiles to/from SD card

The full-featured practice ROM is only usable on Wii VC and a kz-patched version of PJ64. A "lite" version is available for N64, Wii U VC, and normal N64 emulators.

The release: https://github.com/krimtonz/kz/releases/latest
For a full list of features, https://github.com/krimtonz/kz/blob/master/USAGE.md
For installation instructions, https://github.com/krimtonz/kz/blob/master/INSTALL.md