Step one: Sign in like usual.

Step 2: Click the Server list in the upper right of the client.

Step 3: Log out of the account

Step 4: Enter Login info for account 2

Step 5: Rinse and repeat for all your accounts.

While this isn't perfect, and the info isn't saved, this is at least a temporary workaround to play multiple accounts on the new client, without having to use multiple of the clients. I hope this helps some.