Your default Gmail account is what dictates a lot of things.To change your default Gmail account, you'll need to sign out of all your existing accounts and then re-sign in on a browser that will save your preferences; you can then add your other accounts to your new default.
Step 1: You can navigate to your inbox.
Before moving forward, make sure this is your default account.
Step 2: You can click on your profile image.
This can be found in the top right corner of your inbox.
Step 3: You can sign out by clicking on the drop-down menu.
All linked accounts will sign out with your default Gmail account.
Step 4: Click the account you want to use.
Step 5: You need to enter your account's password.
Step 6: Click "sign in".
You can add your other accounts to your new default when you sign into your preferred account.
Step 7: You can click on your profile image.
Step 8: You can add an account in the drop-down menu.
Step 9: You can add an account by clicking the name.
At the bottom of the page, you can add a new account.
Step 10: You can type in the additional account's password.
The email address is required if you're adding a previously unlinked account.
Step 11: When you're done, click "sign in"
Your secondary account should now be linked to your default account.You can link as many accounts as you want.