How do you get rid of a reference material library when you don’t need it anymore in a scene? If you try to delete it, you just get this message “ERROR : Invalid procedure call or argument: ‘DeleteObj’ “.

To delete a reference material library, you have to unlock it first:

– Open the explorer.
– Change the scope to Materials.
– Right-click the reference material library, click Locks, and then click Unlock all levels.
– Now you can delete the reference material library.