I never got that. Why would anyone do it? In Bitwig, when I'm done with sound design and writing loops / sequences, I can bounce them out to separate tracks, pack all the source midi, VST instruments & FX into a folder and disable it which hides it from the view, RAM and CPU. Then I can work with those samples either on the Arranger or - better yet - in Clip Launcher, where I can easily mix & match stuff, group them into scenes to experiment with arrangement order and finally set up some follow actions to have a complete song. Then I can again export the stems - or record/perform the song from Clip Launcher to Arrangement - pack the looping playground into a folder & disable that. Now I can do proper mixing (and "mastering").
And it's all contained in a single project file/folder, where I can always go back to earlier steps if I really needed to.