We have two seperate layers that when combined together inlude the full set of unique ids that we need to search for. There are ids that cross-over between each layer. The Custom URL Parameter only allows for one URL param name. Currently I'm using the "Find" URL paramenter for emedded maps and have two seperate searches set-up in the web map. This works "sort of"...unless there is an address that matches the unique ID.
Allowing multiple parameter names would allow us to create a customize URL that links to out main database. I realize I could merge the two datasets together but our workflow has been set-up to utilize two seperate datasets.