Hi Lucy,
Great to hear it worked for you.
Controls in the report prompt area or the page prompt area automatically filter all objects in the report (or page, for a page prompt) so that is why your drop-down list must be in the body of a page. This is a common issue for users (as a user myself I find it hugely frustrating!) and the dev team is looking into a way to improve that situation. I can't promise this will be fixed, but it is a known issue.
Depending on the version of VA that you have, you might be able to convert the filter to a "common" filter that can be assigned to multiple objects. Using Common Filters
Alternatively, if you edit the filter in "Text mode", you can copy-paste the expression to facilitate making additional copies of it.
Sam
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