How to set up Minecraft Dungeons for modding (Launcher version)
https://dokucraft.co.uk/stash/?help=modding-dungeons-launcher

Open the launcher and click on Settings in the lower left corner.
Go to the folder shown in the Settings menu under "Minecraft Dungeons Installation".
From the install folder, go to dungeons\dungeons\Dungeons\Content\Paks
Create a new folder here called ~mods (Yes, with a ~) and put your mods in this new folder.

When you want to launch the game, do it by running the Dungeons.exe file in your <install folder>\dungeons\dungeons folder. Running the game through the launcher will remove any mods you have installed.

How to set up Minecraft Dungeons for modding (Windows Store version)
https://dokucraft.co.uk/stash/?help=modding-dungeons-windows-store

Dokucraft Dungeons