BugBug brings you freedom in editing your test cases - you can start recording from any step in existing test case!
Just go to a test case view and:
Hover on a step you want to record from
Record from here option
The recording window will open and you can proceed with the steps you need to record:
Of course you can also continue recording from the current end of a test case - here you find helpful button
Record from here in the end of test case view.