De acordo com a página oficial do Google, não é possível usar o Google Drive para seu Mac / PC com mais de uma conta ao mesmo tempo: Alternar entre várias contas do Google Drive - Ajuda do Google Drive
It's not possible to use Google Drive for your Mac/PC with more than one account at the same time.
If you want to use Google Drive for your Mac/PC with a different account, disconnect the account you're signed into and sign into another account. We don't recommend doing this frequently, as you'll need to create a new Google Drive folder every time you switch accounts.
Outro usuário postou uma solução ruim (na minha opinião):
Setup multiple user-accounts on your computer, setup Google Drive client software under each user-account, syncing with a different Google account from each one. Share the folders with your main account. As long as you keep the other user-accounts logged in, Google Drive will keep syncing for all the accounts you've set up.