[6.x] Floating toolbar pointer improvements

[JayGeorge]

Description of the Problem

I noticed that the floating toolbar blocks pointer events underneath it's invisible parent container

Here, for example, you cannot click "Whistler's Mother and more"; the invisible horizontal container of the toolbar is blocking it

What this PR Does

• Unblocks pointer events on the parent, re-adding them to the inside container
• Replace a hard-coded z-index while I'm here

How to Reproduce

1. Try selecting something underneath the toolbar
2. Experience not being able to select anything