@Peter – in InDesign's GUI? I think, you cannot…
But there is a workaround. Just copy/paste the index marker to a new, fresh document.
Then you can lookup the topic there. It will be the only one in the Index Panel.
I will ask my Designer about this approach but my reaction is that this would not be feasible if there were hundreds of potential items in the manuscript with markers that could extend to one or more words?
@Peter – the markers do not "extend" to words or ranges of text.
They just point to entries in the index. You could easily edit the index entry (a topic) and there will no semantically correct connection from index marker to index entry.
Don't know what you like to achieve here specifically.
Compare position of index marker (and the surrounding text) to the contents of the topic in the index?
On case by case basis? And the possibility to edit the entry in the index directly when selecting the index marker? Or moving the index marker to a different position?
In InDesign's GUI you could do the following:
Open the Index Panel, select the page number of the topic and chose to go to its index marker. Now decide what to do. Editing the topic, moving the index marker etc.pp.
@Pickory – ah!
You are working at it.
A new plug in… ?!