YouTube login with Gmail account

Google has enabled multiple sign-in with the use of Switch Account. YouTube also supports this ability to switch between accounts.

For Gmail

1. Login to Gmail
2. Click your full name or email address in the Google bar.
3. From the dropdown menu, click Switch account or Sign in to another account...

For YouTube

1. Click your username in the upper right hand side of the page
2. From the dropdown menu, above sign out, click Switch account.

Once you're logged in to both accounts, you'll be able to go back and forth between them without having to log out and log back in with different accounts.

The only way to do this, is if your account was created before May 2009 via the unlink option, otherwise you will encounter the following message

Your account is permanently linked to a Google Account

So that is that, there are no tricks around this one as this "issue" has been around for years. I have tried deleting accounts and getting the unlink option to work. I have read most if not all forum posts. This is Google's stance (whether by design or choice) and it does not look like it will change anytime soon.