Thanks - its a great suggestion but I don't think I have anything that I can uniquely identify the whole group with. I wish I did as that would be perfect! I am moving a range of test cases from System Testing to SIT/E2E and although I have utilised a lot of the different category fields, the mix of tests that need to move is too random. Unless I can create a filter based on a list of Test Case ID's? Is that possible?

If you have to manually select the testcases a work-a-round for filtering could be a temporary category:
Create a test case category "Move" with values yes/no
For all test cases which should be moved assign yes (mass updates are also possible if you have at least a partly-filter:-)

In case you do not use the priority field of a test case you could also use the priority. and mark all test cases which should be moved with prio high,...

   Cheers, jörg

Thanks again - some more great suggestions, however, I currently have just under 1200 test cases in this test plan, and in order to add a temp category I'd still need to search by the test case ID in order to update each one or even if I used priority (I have already used that field anyway), Looks like its manual job! I have an Excel spreadsheet that has all the TC's from the plan and a column in there that says whether they need to move or not, so that is how I have the TC ID's. It would be great if you could query/ filter a list of TC ID's but I don't think you can put more than one TC ID into the ID field in the filter?

OK, I think you have helped identify the quickest way I can manually update it. In the test plan I am moving them away from, in the test cases section, I filter on the TC ID, then edit the Category field (from System Testing to SIT/E2E), the once I have gone through and updated those, then I can filter in this test plan to find all the test cases that have a category of SIT/E2E and remove them from the System Test Plan, then I can go to the new test plan and add them by using the same filter query. Still a bit manual but a lot quicker than editing every test case one by one. I can also then go to the test execution records and filter by the same thing and change the test plan associated to the execution records. Thanks for your help :)

If your testcase ids are available in Excel you can also use excelimporter.
At the end you need only a list of text case ids and a config *.cfg file.
Within the config file you can assign the (temporary) category a "yes" value.

   Probably this is the quickest way .-)

   good luck, Jörg