You just add the field to the button URL. The code below will add a new record to your table and fill out what ever fields need to be brought over.
URLRoot() & "db/" & [_DBID_DOCUMENTS] & "?a=API_GenAddRecordForm&_fid_15=" & URLEncode ([Record ID#])&"&_fid_11=" & URLEncode([Related Client])&"&_fid_13=" & URLEncode ([Related App])& "&z=" & Rurl()
Let's break that down:
URLRoot() & "db/" & [THIS IS THE NAME OF YOUR TABLE THAT YOU ARE CREATING A NEW RECORD FOR] & "?a=API_GenAddRecordForm&_fid_THIS IS THE FIELD ID ON THE CHILD TABLE THAT DIRECTLY RELATES TO THE TABLE THE BUTTON IS ON (PARENT RECORD ID#)=" & URLEncode ([Record ID#])&"&_fid_THIS IS ANOTHER FIELD THAT YOU WANT FILLED OUT WITH SOMETHING FROM THE PARENT TABLE=" & URLEncode([NAME OF FIELD IN PARENT TABLE])&"&_fid_13=" & URLEncode ([Related App])& "&z=" & Rurl()
You can just keep adding fields to auto populate from the Parent Table.
You can find the NAME OF YOUR TABLE in the table's "Advanced Settings"
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QuickBase Girl
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