To switch to another MT5 account already logged in on MT5 desktop, please refer to the following steps:
Step 1: Open MT5 on Desktop, click [View] - [Navigator] on the toolbar, or use the shortcut key "Ctrl+N" to open the Navigator box.
Step 2: In the [Account] section in Navigator, to access the already logged-in account, double-click [Account].
A list of already logged-in MT5 accounts is displayed. Double click on the account you want to open.