Automatically apply style depending on what section of document a heading is in
Hi
I use the Table of contents function a lot but have a new challenge I can't figure out.
I want to have a table of contents on a Master, so that it appears as a Sidebar on every page of the document (brand guidelines doc). Then I want each heading in the sidebar contents to look 'active' or not depending on which section the user is in. Here's a quick mockup to explain what I'm after.

Is there a way I can set the style to automatically change depending on which section of the document it's in? e.g. using GREP maybe? or combined with section markers?
Any help is appreciated.
Thanks!
