Hiding items in clipspopupbody catalog and own files

Can't figure out how to hide some things with display: none without affecting the other.

In #clipspopupbody_catalog everything is fine as is.

In #clipspopupbody_ownfiles we want to hide all of the other items in local_table_clipspopup_mainsections except the heading but not affect #clipspopupbody_catalog.

I guess I don't know how to target ID's within ID's

"except the heading" means you want to remove all the button but leave only you head text line?
Target things into things is easy, that's actually what the CASCADE od CSS stands for.
For example, if you'd use this you would hide every time the entire local_table_clipspopup_mainsections block:

#local_table_clipspopup_mainsections {display: none; }

If you'd like to do the same but only when it's included into #clipspopupbody_ownfiles, then the syntax is:

#clipspopupbody_ownfiles #local_table_clipspopup_mainsections {display: none; }

Basically, if you have space separated selectors (can be IDs buyt also classes and everything else you normally use in CSS), then it applies only onselectors that are included in the leftmost selector.
So, you if have something like this:

#clipspopupbody_ownfiles td a {color: red; }

this would color in red only links that are into a TD tag that is included into a tag having clipspopupbody_ownfiles as ID

Makes sense?

Makes perfect sense. That is what we tried without success. But, now with your confirmation I remembered that we have Test Style To Use in play. Dang it! Hopefully this helps others too. Appreciate the assistance.