I wanted to delete all subsequent occurrences only and retain all previous ones. I clicked delete ALL option in hope/expectation that I may get a choice of ALL or Future but they have all disappeared from the calendar. I have not closed the Thunderbird application hoping a quick fix is possible. Is it??

Note for future upgrades: The need to delete future occurrences only is desirable for the the retention of past actions and would be quicker than deleting one at a time.