Over the past few months, I and others have been working on a ROM editor for Pokémon Mystery Dungeon: Rescue Team DX. It's still very much a work-in-progress, but there's enough there to warrant a thread about it.
This ROM editor has two target audiences: users and developers. For users, it's designed to be as easy to use as possible. Just give it your already extracted ROM (this will be made easier in the future), and follow the prompts. For developers, C# and Lua can be used to make more advanced changes, while being able to distribute your work to users, without making things any more complicated than what's shown in the below User screenshots.
The UI is designed to be as simple as possible, guiding you through the editing process without hand-holding. Screenshots:
The tutorial for users includes a step to choose a modpack. This is where developers come in. Using the built-in mod support, you can use C# or Lua scripts to automatically change things not present in the UI. Example use-cases:
Addition of model data that's not already present
Randomization of data such as playable starters
Bulk alteration of stats that would otherwise be impractical to make with a UI
See the readme in GitHub and the sample mods in the console app project for more details. A standalone package to create mods is planned but not yet available.
Also note that because the editor is in active development, things like namespaces and method signatures are subject to change. If this impacts you, please let me know so I can know to publish breaking changes somewhere. This post will be updated when this is no longer the case.
This ROM editor is not yet ready for widespread use, but should otherwise work fine.
Source Code: https://github.com/evandixon/SkyEditor.RomEditor.Rtdx
Prerelease binaries of the UI can be found here:
Look here for additional binaries, such as that of the console app.