Help please! I’m trying to build a saved search for journal entries that contain a specific account. The result should show all lines in the JE transaction, but instead what I’m getting is only the lines with account I’m looking for.

You could take the document number of the journal entries returned and do a lookup to another export of all JE lines, more manual but would get you the desired result

There is "Account (Main)". Select that as the account you want.