This sub-issue is part of #66377

What problem does this address?

When comments are present in the sidebar, it's not always obvious what block the comment is related to, as there is no visual indicator on the block whenever the comment is selected.

What is your proposed solution?

When a comment is selected, the related block in the editor should also be selected or have some kind of visual highlight to indicate that it is the block that the comment is related to.

When the comment is deselected, or another block is selected from the edit screen, both the comment and the block related to the comment lose focus.