I made this a while ago using applescriptobjc.
It is a utility application that acts like a find and replace dialog for InDesign objects.
You specify an object to replace, and a replacement object.
When you click ‘replace’, the application scans the document/spread (you specify) looking for matches, then asks you to place a new object over an old one so it knows where they should be relative to each other.
Then it replaces each instance it finds.
In my use (over about 18 months) I’ve never found it to make an error, but it has not been rigorously tested.
You can see the git repo here.
A compiled version is here.
