Synology: password change for users with restricted access

I use the cloud drive feature on my Synology NAS. I have a couple of users who have only access to the Synology Drive cloud service (no DSM, no FTP...). I've created the users and gave them unique passwords. Now I'd like to offer the possibility for my users to set a password of their choice.

Is it something possible (it seems to be a feature that you can have if the user has access to the DSM)? How to do it?

Thanks.