didwal If you are happy for your users to save the passwords in a password manager or their default browser, once the accounts and passwords are set, they do not need to enter them except the first time they log into their profiles.
Grommunio Files is basically a modified version of Nextcloud, and all the Nextcloud clients work with Grommunio Files, so they can be set to login with the user. Also if you open the Grommunio Web client, then go to settings you can add the Files add in (where you can add the users login details) and Files will be available via the web browser client. So lots of ways around users having to login twice.
Hope this helps.