If you want to manage your y0utube brand channel under another gmail, it’s possible. You’ll just have to connect the channel with that particular gmail id, that’s all. There are two ways of doing it; one through y0utube channel itself, another through the associated google+ account.
Advantages of connecting a y0utube brand channel with another gmail
If your y0utube channel is a brand account, then you should associate it with another gmail. Because, God forbids, should your primary channel/account ever get terminated, you may lose access to your brand channel as well, unless it is already associated with another gmail.
When my first primary y0utube channel was terminated back in March 2016, I lost access to the associated brand account which I designed as a ‘ghost stories/paranormal activities’ channel. I uploaded a couple of videos onto that and it just started to gain views. Then all of a sudden this unexpected incident (termination) happened and I was dumbstruck. Later I found a way to associate that brand channel with another gmail in order to manage it; because once you lose access to y0utube under a particular google/gmail account, you can no longer use that gmail to manage any brand channels associated. This type of thing happens when your primary/personal channel is terminated. To know more details about the difference between primary and brand channels click on the following link.
How to add or remove managers of your y0utube channel
Here the word ‘managers’ doesn’t necessarily mean different people only. It could be different people (like you and your close friend) or different gmails owned by the same person (you). In order to add or remove such managers you need to click on the channel icon which would be in the upper-right corner of the screen while you’re on any page of your channel. When the popup menu appears, just click on the gear icon on it, you’ll be directed to your channel’s account page with url https://www.youtube.com/account.
Now click on the blue ‘Add or remove managers’ link which you’ll get to see in almost the middle of the page. You’ll arrive on a page which doesn’t actually belong to y0utube, but to your google account in general.
Now you need to click on the big blue ‘MANAGE PERMISSIONS’ button, upon doing so a dialogue box will appear which will show your personal/primary y0utube account (which is yourself) as the primary owner. So now it’s time to assign another owner (which could most certainly be another of your gmails). To do that, you just need to click on the ‘+’ sign which would be in the upper-right corner of the dialogue box (this sign is followed by a ‘human/person’ symbol).
Upon doing that a submission(input) box will appear where you have to type either the secondary owner’s name or their gmail address. I prefer to type gmail id in this case, because these are more precise (totally different from one another). Also you need to assign them a role as owner, manager or communications manager. If the secondary gmail belongs to you, then you can assign it as ‘owner’. Be sure to choose a very faithful and trusted person to assign this particular position; just remember that one owner can cancel out another owner. If you assign one of your friends as ‘manager’, then they will most possibly be able to do all the things that you’re capable to do except for deleting the channel or assigning another owner/manager.
Whatever, after typing the gmail and assigning the role hit the ‘Invite’ button. You’ll see that gmail-holder as ‘Invited, owner’. They will have to accept your invitation, otherwise the process will not be completed. If it’s you who is accepting your own invitation, or someone else’s; then go to your particular gmail account. Open the mail containing the invitation and accept it. When you click on the big blue ‘Accept’ button, you’ll be directed to a google account page where you’ll have to press on the ‘Accept’ button once again. This page will show who’s (with what gmail id) inviting you to manage what brand account as which role.
When the assignment is complete
Now there might be a question as to how you know whether the role assignment process is complete. When the invited person (you or your close friend) has accepted the invitation, you’ll receive a mail on your gmail confirming that. Also when y0utube will be accessed from the other gmail id, your brand channel will show on the list of the popup menu which appears upon clicking on the channel icon. Now it will be possible to switch between that brand channel and any other brand/primary channel, as expected.
How to assign another gmail to manage a y0utube brand channel when the primary one is already terminated
Now this becomes a great problem for many YouTubers when their primary channel is terminated and brand channel is intact. Since their y0utube access is denied, so there’s no way they could manage that brand channel using that gmail. Well, there is a remedy to their problem; they could now assign that channel to another gmail/google account. In order to do so they’ll just have to go through the following steps.
First visit this link with url https://myaccount.google.com/brandaccounts at the lower portion of the page while you’re logged into the Google account which has its primary y0utube channel suspended. You’ll get to see your brand accounts. Now click on the right-facing arrow associated with your desired brand account.
You’ll arrive on the google page where you can assign new people/gmails to take care of your y0utube brand account, the page with the big blue ‘MANAGE PERMISSIONS’ button. And you know the rest (what to do) unless you haven’t gone through the above paragraphs carefully.
There’s most probably another (a third) way to assign the brand account a new gmail id, it’s through the associated google+ page. Once I went through this procedure for one of my brand channels whose primary channel had already been terminated. But the process I just showed here is meant to be easier, so I prefer not to describe the ‘google+’ procedure. Nevertheless you could try that and let me know whether you were successful in doing that, in the comments box.