I have two lists: List A and List B. List A has Project Number column (Single line of text) and List B has Project Number column (Lookup Column) pulling data from List A. For List B, I have SharePoint integrated form and in that form for Project Number(Lookup Column), I want to show only Project Numbers that are in List A but there is no existing item of same Project number in List B (i.e. the Project numbers that are in List A but not in List B). I need help in filetring the project Number. Should I create a collection for List B Project Number column so filtering doesn't impact the form performance. I am also trying to avoid delegation in Filtering the Project Column.
I appreciate any help on it.