Yes, this is possible in both apps and achieved through the Settings page.
For iOS, the Settings page can be found by tapping the Settings icon in the lower app menu bar.
For Android, the Settings page can be found by tapping the menu icon on the home page and selecting 'Settings' from the menu.
The app will show you which account you have currently setup.
To add another Datto Drive account, select 'Add new account' or 'Add account' and you will be presented with the login screen.
Simply login with the other account and it will also appear in the Settings page.
The app will not combine all the folders into one view, but you can select which account to view by tapping the radio button beside the account name on the Settings page.