The Kunena team has announce the arrival of Kunena 6.2.6 [K 6.2.6] which is now available for download as a native Joomla extension for J! 4.4.x/5.0.x. This version addresses most of the issues that were discovered in K 6.1 / K 6.2 and issues discovered during the last development stages of K 6.2
Topics that are moved into this category are generally considered to be closed. Users may want to add additional information but these topics should not be resurrected in order to discuss new problems or unrelated matters.
SInce this is an automatic sequence number from MySQL, this is no as easy at the moment. I recommend you create Brand New Categories, leave them empty, go into phpMyAdmin, edit their category ids to your liking, check your forum if they are what you want them to be and then move all messages into the new categories.