Yes, you're right, the idea is that the population and its subdirs are only created when needed. So this fix is nice, but even nicer to remove this folder creation out of general files and manage this within the individual wrappers that need these folders to exist.

The issue was not xASL_init_FileSystem but xASL_init_DefinePaths I believe, that creates everything upon initialization. Easiest fix for now is to move the contents of xASL_init_DefinePaths from line 81 onward (loop of xASL_adm_CreateDir) to the start of ExploreASL_ProcessMaster.

When data is loaded, it should define the paths, when data is processed (i.e., running ExploreASL_ProcessMaster) it should create the folders. Is this the case now, that ExploreASL_ProcessMaster is only run when processing is set to true, and this creates the folders?

I agree in principle. xASL_init_DefinePaths should not create anything - but this is already fixed by Michael. All directory creation is done in xASL_init_FileSystem - this is then called from all modules (ASL, structural, etc.). So it is now indeed only run when the processind modules are run. It might be possible to move all this from these modules to ExploreASL_ProcessMaster if needed - but not sure if this wouldn't have any complications.

Anyway - the things already seem to be done according to what we want... Can we merge?