Hi @LIZDean
Unfortunately, to my knowledge, this is not yet possible and might be something worth raising within the Ideas section of Esri Community.
Within both the query and filter widgets, you can set up queries/filters for multiple different layers and allow your users to select which ones they would like to interact with. You can then also set up the SQL expression so that it "Asks for values" so that the user can select the attribute they'd like to filter in the particular field the expression is set up for.
Currently, however, users do not have the ability to fully configure this SQL expression on the fly, so they cannot select the field they would like to filter by for example.
I hope this makes sense, do let me know if you'd like any further clarification.
Thanks,
Issy