Is there going to be a category for the bonus despair dungeon minigame?

There already is in the Sub-games tab, two below Forum.

DDMT can also be found in the DR series page by toggling Unofficial Releases, which will also display the minigame in DR2 and a few fangames.

Here is the URL for DDMT, though: https://www.speedrun.com/drv3ddmt

Ye