In Ecamm Live v4.0 and newer there is no longer a need to switch YouTube channels, because you can stay logged into both at the same time.
To do this go to the Create New Broadcast window by clicking on the blue New button in the bottom right-hand corner of the Main Window. Your currently selected streaming destinations are listed at the top.
To add another YouTube channel, click the + Add button and then choose Add New Destination. A new window will prompt you to pick a streaming platform. Select the YouTube icon and you will be promoted to login to your YouTube account.
You can connect as many YouTube accounts as you want, and select which one you're streaming to by adding or removing them in the Create New Broadcast window.
Remove the channel you don't want with the x button.
Add the one you want from the + Add button.
You can also stream to move than one destination at the same time with our multi steaming feature. Learn more about it here.