@Jet-Huan

You need to setup your swiftmailer(responsible for sending emails) and once done whenever you add a customer or agent they will receive a email for the same for setup password.

But if emails not working for you the you can enable option for admin as well to setup password.

You can achieve this by simply made few changes.

For changing password for Agents:

locate path in your project:

vendor->uvdesk->core-framework->Resources->views->Agent->updateSupportAgent.html.twig

open this file reach to this section https://github.com/uvdesk/core-framework/blob/master/Resources/views/Agents/updateSupportAgent.html.twig#L142-L160

And replace:

{% if userDetails and userDetails.isVerified %}

BY

{% if user_service.isAccessAuthorized('ROLE_ADMIN') %}

For changing Customers password:

locate path in your project:

vendor->uvdesk->core-framework->Resources->views->Customers->updateSupportCustomer.html.twig

open this file reach to this section https://github.com/uvdesk/core-framework/blob/master/Resources/views/Customers/updateSupportCustomer.html.twig#L82-L100

And replace :

{% if userDetails and userDetails.isVerified %}

BY

{% if user_service.isAccessAuthorized('ROLE_ADMIN') %}

once done clear your project cache by:
php bin/console c:c

Finally check admin will be able to update the password for agent and customer.