Do you mean "Group Clip By?"
Select the "gear" icon under the Event Library and there's Groups Clip By and you can set that to None.
I think this is the one you mean since it appears under Name.
Or Column Header?
If you're looking in the Event Browser if you click on the bar where it says "Name" etc (your column headers) you can right click and deselect the columns you don't want. You could, for example Hide All Columns and the add back the ones you want.
BTW the awkward nature of the nomenclature in FCPX is one of my peeves. It's really hard to communicate things by what they're called in FCPX so one has to resort to physical descriptions.