How to Change Your Default Google Account on the Web
It’s easy to use the web with multiple Google accounts signed in at the same time, but you will always fall back to the “default” account. It’s a little tricky to change this, but it can be done.
The default Google account is determined by whichever you first used to sign in. This same rule applies to Android devices and many Google apps. Unfortunately, changing which account is the “default” is a bit cumbersome.