From the hosting service, to have access to the domains and websites that are within the subscription.

If for some reason 'sub.example.com' was added to Plesk as domain the wildcard certificate for 'example.com' doesn't cover it and it is required to issue separate certificates. Please add an ability to convert existing domains like 'sub.example.com' to subdomains of 'example.com'.

Please add an ability to hide the following warning in case the changes were applied to a particular domain intentionally:

Warning: The DNS zone was modified. If you would like to apply changes in the DNS template to this zone, either click the 'Apply DNS Template Changes' button on this page or go to the Server Administration Panel > Tools & Settings > DNS Template Settings > Apply DNS Template Changes and choose the 'Apply the changes to all zones' option.

It would be good to add the ability to manage "Smart static files processing" option through Service plan settings. Since this option is enabled by default, it might affect some applications.

It would be nice for the users to be able to enable or disable:

"Permanent SEO-safe 301 redirect from HTTP to HTTPS"

option in their panel.
Instead of setting it in the service plan, give to the user the permission to manage this feature.

Due to security reason users may need to ability to protect their archives with password. Currently there is no ability to extract or create such archive. Please, add

To Analyse the DMARC reports DMARC monitoring tool should be available in Plesk for each Domain at least & for all the subscriptions of the server.

in Event Manager, we can select parameter of "Username" only when user login failed and select parameter of "contact name" only when user completely login/logout. Users is asking me that why we didn't use the same variable (Username or contact name, and I preferred username) and more information should be added for security issue (eq. IP Address)

[refer document]
https://docs.plesk.com/en-US/obsidian/administrator-guide/server-administration/event-parameters-passed-by-event-handlers.67897/

It would be nice that you can sort on 'Valid to' with in the advisor section secure websites with ssl/tls certificates.

It would be nice to have the powerful OpenWebAnalytics integrated by default in domains:

http://www.openwebanalytics.com/

It's the only open source web analytics I have found that includes heatmaps

Improve the email notifications management through CLI using the "plesk bin notification" command.

As of now, there are plenty of notifications that can be easily managed in Plesk GUI while it is not possible through that command making it quite hard to manage as the ones that can not be managed through the command itself, need to be modified directly on the Plesk database while in Plesk GUI all (or almost) the notifications are unified under Tools & Settings > Notifications

Cpanel does have a feature where if you mount your additional disk under /home2, it will start saving accounts there if the main disk (/home) gets full.

The idea is: Use 2 Vhosts or more with different drives with Plesk.

With current version, to get all subscriptions that will expire soon must request all subscriptions, include the limits dataset, and then perform a filter.
Leaving the possibility to filter by expiration date will be a greate improvement.

The LDAP Auth extension only allows enabling LDAP authentication to Plesk. Can you allow end-users to use outlook/thunderbird/webmail with the password stored in the Active Directory?

In this case, the mail server has to be configured via Plesk to use the LDAP authentication.

In Plesk, there is no CLI for managing scheduled tasks. Thus, if it's necessary to create multiple scheduled tasks, it's required to create them one-by-one in GUI.
CLI for managing scheduled tasks will allow creating multiple scheduled tasks by invoking a CLI utility in a script.

add search feature to File Manager. Can't believe it's not here but I can't find it. Is sorting by name the only way to find files when there are thousands?

Allow configuring Smart Updates to check process such as the Checkout when Wordpress is used as an online store (WooCommerce) so it ensures that performing the upgrade won't break the checkout process from beginning to end.

And/Or allow the ability to configure custom testing scenarios.

Limit the FTP Access to a specific IP range or IP for a specific subscription:

Ex:

Example.com / IP 10.0.0.1 allow only connection between 10x to 30x IP