World shaders disapearing in Blender File In shading tab I created two settings for the world. One for a night, one for a day, 
but one is always disappearing after I reopen the file.

Is there a way to keep them both? I tried solving it this way:

However settings are suppose to be linked to 21 files. When I change something in the settings I have to append it in 21 files and I'm sick of that.
Blender By default purges most unused data blocks. (this happens when you save and reopen the file)
Just add a fake user and it should remain in the file until it has no user (be it fake or not) and you save it or manually delete it.