rml_folder=(folder ID) not working

I am using the free version of Real Media Library and when I use rml_folder=21 which the url of library folder I get a No Posts message. I have worked round it by assigning a unique category to the pdf files in the folder e.g [medialist globalitems=1 mediatype=pdf category=BuildingInspection style=ml-white] however, as I cannot bulk assign the category. The only bulk action that is shown is Delete so it seems I need to edit each file to assign the category.

Otherwise the plugin seems great for what I need and so please I found it as I’d like to use it elsewhere to automatically add files to our archive lists.