Restrictions on creation of symbols

hi all -

I have a page that has two collection list, one of which has a sub-collection (child) list within it. It works fine, but I also have that identical setup on another page so I’m starting to have to cut/paste each time I update the design.

I thought to put the whole thing into an element, but when I right click on the wrapper it won’t allow me to make an symbol. Webflow allows me to make an symbol out of the first, simpler collection list item. But, then I can’t make a second symbol out of the other collection - the one with the sub-collection.

I am trying to understand what the rules are around symbol creation but not finding it. Can anyone help me understand what is possible?