If I want to restore all files of a domain because the website has been hacked.... default restoration will simply overwrite existing file.

In the cased of a hacked website, hackers can add suspicious files on the domains and those files won't be remove upon restoration.

It will be great to have an option allowing us to opt for a purge before restoration so that we can completely replace the files, databases, etc. and not simply overwrite existing files.

Backup / Restore manager is fine, but what if we only want to restore one / several tables, not the whole Database?
Add feature to restore single tables only.

Or even more flexible: add the possibility to restore a DB dump to a file. This file can then be searched / adjusted to restore specific tables only. Once it is adjusted we could load it in the DB / perform the restore.

At the moment the extension order of Plesk multi-volume backups is the following:
<DateFormateHHMMss.zip>
<DateFormateHHMMss.zip1>
<DateFormateHHMMss.zip2>

This means that volumes .zip1, .zip2 can not be extracted after their downloading because they have an incorrect zip extension format.

The idea to change the extension order of Plesk multi-volume backups to:
<DateFormateHHMMss>.Zip
<DateFormateHHMMss>1.Zip
<DateFormateHHMMss>2.Zip

That the multi-volume backups have the correct zip format and can be extracted.

Please add differential backups.

Currently, Presence Builder attachments (for example, images that have been added via Slider module to a domain) ends up in every incremental Plesk backup. Such attachments should not be in incremental backups as they are not being changed, modified, etc before the incremental backup starts.
I suggest adding such a feature for incremental backups support for such Presence Builder files.

I suggest adding functionality to restore a domain or subscription from a server-wide backup on the Plesk server, where this domain or subscription is missing (for example, it was deleted before). This is very inconvenient when you have to create a nonexistent subscription, then restore it, and then separately restore the domain in it.

Add a possibility to store backups on Linode Object Storage. As it is done for DigitalOcean Spaces, Amazon S3 Backup, Google Drive Backup

Exclude mailing lists from incremental backups

It would be useful to be able to remove from a server-wide backup only particular domain's data (such as mailbox accounts) as it will help to manage server's disk space in a more efficient way and store only needed data

According to https://support.plesk.com/hc/en-us/articles/360007305893 , it is required to enable resume uploads on FTP server side, however, it would be nice to have the option to disable resume uploading from Plesk side in case if there is no access to FTP server

Plesk does currently only support Amazon S3. Amazon Glacier is cheaper than S3 and also good for backups. Also support for Google Cloud would be great since at the moment, Plesk does only support Google Drive which is no professional backup (example: https://github.com/plesk/ext-cloud-backup-example).

Currently, restored backups, which have been downloaded from a remote storage, are being stored locally and appear in the backups list and become part of a backup process.
Expected behavior:
Download, restore & delete downloaded backup files. Remove from the backup list.

Add to Plesk functionality to allow the clients to restore the backups on the remote server via FTPS.
The administrator can create backups and clients can restore their own parts of backups. As how it is done with common backups on local storage

There is no option to encrypt backups. I do not trust Google or any other cloud service. Yet I could use the (otherwise completely useless) storage to put my backups there.

So please include a proper and secure encryption. Thanks!

Edit:
It could be as easy as running gpg as a last step before uploading:

Encrypting (simple tar example):
tar -czf - [FOLDERS] | gpg -c --batch --passphrase [PASSWORD] -o backup.tgz.gpg

Decrypting:
gpg -d --batch --passphrase [PASSWORD] backup.tgz.gpg | tar -xzf -

If you do not want to use FTP or SFTP you can also use Samba

I'd really like to have a UI to select what is contained in a serverwide scheduled backup.
We have a couple of domains where people dump photos and videos for further processing, amounting to 100s of GBs, and we don't need backups of those.
The UI you got for the restore dialog would be just fine.
I think it makes more sense to select what is contained, than what to exclude.

The Backup Manager should be able to show the backups of all domains below the admin, including resellers.

Would love to see Rsync support added. SFTP is slow.