How do I change where a GL code appears on the P&L?

Accounts → Settings → P&L Mapping. A rule names a prefix, an exact code or a range and the P&L category it belongs to. Your rules are marked as yours and sit above the platform defaults; a code no rule matches falls to the standard layout. Every report, pack and draft reads the same mapping. The setup step counts as done once you have at least one rule of your own.