Seems good to me. We are talking about the query tool, right?
Right.
Be careful
that users may have many query tool windows open at the same time.
Actually I thought of something simple.
One file per window, when the window is closed, the pgAdmin will delete it.
We avoid the loss of query, when the pgadmin crashes or because of a power outage.
So, when the user open the window, the pgAdmin will ask to the user if he wants reopen the file found by pgAdmin.
If the user answer is NO, the pgAdmin will delete the file.