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phpMyAdmin version upgrade is not recommended.
phpMyAdmin is a part of Plesk core packages, and only versions provided with Plesk itself can be used.

If you really need to upgrade it though, it should be done at your own risk, since phpMyAdmin scenario is not supported by Plesk and thus, it is not covered by Plesk Technical Support.

If you still encouraged to perform this upgrade I strongly recommend you performing it first on the test environment, that is similar to your current server.