Group Filter/Sub-Group Filter/Sub-Folder Question

[NicholasMorgan]

Hello Everyone,

How do I move an already existing group filter underneath another group filter to create a sub folder type structure. 

For example: I have a group filter called Columns with layers inside it. I created a new filter called Structural and I want to move the already existing Columns 'folder' (it's really a group filter, but I normally refer to it as a folder) underneath. This would make the Columns folder act like a sub-folder.  How do I do this? I cannot seem to just drag and drop and I don't see anything under a drop down menu. 

I know how to make sub-folder type filters when I create a new one, but I want to make an existing filter become a sub-filter.

Thanks,

Nicholas