https://furka.github.io/40k-10th-list-builder/
It supports all factions (including forge world) and lets you adjust which models are in your personal collection.
(source code: https://github.com/furka/40k-10th-list-builder)
Okay, I have been playing around with it a little bit, and its just amazing, probably the best list-building option for 10th edition right now
Wargear/Weapon Loadouts would be amazing