This is an SKSE plugin that can be used to launch BodySlide while Skyrim is running so you can make changes and see the results while the game is running. The default key to launch BodySlide is F2 but this can be changed in BodySlideLauncher.ini to something different if you prefer. Also, the 64-bit version of BodySlide will be launched from the default installation location, but if for some reason you have BodySlide installed to a non-standard location you can set the path in BodySlideLauncher.ini as well.

This works best when you are running Skyrim in borderless window mode so you can quickly ALT-TAB between BodySlide and Skyrim. Both outfits and the player character body can be changed with this. If the outfit you are changing is equipped then you won't see the changes until you unequip and then equip the clothing again. It is probably best to make changes in a location without any other NPCs to make sure Skyrim isn't keeping the old mesh in memory if other NPCs might be using the same outfit. Also, if the original meshes are in a BSA file and you are creating the loose files for the first time you may not see changes until the next time Skyrim launches so it can detect the loose files.