Hey.
WonderfulWhims does not work with Legacy version of The Sims 4, nor are there any plans to create a Legacy version of WonderfulWhims at the moment!
Due to WonderfulWhims not being the main mod I develop, the legacy edition of the game requiring a separate code base to develop on, and the need to switch between regular version and legacy edition, the development of a legacy version is way too much hassle. One will come when I'm confident the mod is stable with all of its features, as I will then no longer update it with new features.