How do I create custom formations? e.g class 170 2car variant, EMT class 158 3car variant, class 43 hst emt single powercar (formations that cannot be created with formation designer)
Create a plugin, create folders as necessary, in the context menu for the folder where you want the formation to be, select new > miscellaneous > data asset, select train formation, open and edit. Or just duplicate an existing one as a starting point and edit that.