How To Add Secondary Google Accounts To Default Accounts
Step 1: Open Google Account Settings
On your browser or Gmail application on your device select the default account which is already signed in and then click on the profile icon (this will open the menu of all the accounts which are already logged in) and select Manage your Google Account or Data and Personalization to access account settings
Step 2: Access Personal Info
Under the personal info & privacy section, click on Your personal info, then scroll down to the Email section.
Step 3: Add and Verify the Secondary Account
Now, under the Alternate emails section click on Advanced then click on Add Alternated email.
Enter the email address of the alternate email account that you wish to add.
Follow the prompts to verify the ownership of the secondary account.
Remember: You can add any other account which is not a Gmail account , and it should not be linked with any other Gmail account at the same time.
How to Change Default Gmail Account
A person can have more than one Gmail account logged in web or mobile phone. The default Gmail account is the primary email address linked to a user’s Google services. It’s the account Google uses as the default when accessing various services like Gmail, Google Drive, and YouTube. Changing the default account allows users to manage their online activities more effectively.