Improve documentation on Test import/export

[lampajr]

Feature idea.

The current documentation on the Test import/export is lacking some important bits with regard what users should do to properly export and then import the test as duplicate one. Moreover, with #2257 we slightly updated some aspects of the import process that should be reflected.

Describe the solution you'd like

Improve the Test import/export documentation by providing an example of how users could duplicate Tests using the export/import feature.
Be sure to include all manual steps that are required from user standpoint, e.g., clear some ids and etc.

Additional information

Suggested #2257 (comment)

[lampajr]

Also consider this change #2264 when updating the documenation