I understand the limitation of not being able to go back, however I have backup copies of all my personal libraries and I use Kicad as a hobby not any type of critical project.
So, I guess the short answer for you (since it seems that the intention of your question was thinking ahead to when you shift up to KiCad6) is just open your library in v6 and then save it out again. Shouldn’t be too tedious with a small handful of personal libraries.
Keep in mind that the KLC are reasonable but arbitrary rules to make the maintenance of official libraries possible (and to keep the few surviving maintainers sane, I guess). They are also practical for version control and to keep things in order. But they are not required for personal libraries, and they are currently not compatible with international standards, if that would be a requirement.
Thanks to all. I have since sorted out my procedural error and have now converted my few libraries to “V6”
Just of others who may read this thread:
My “personal” libraries and not in any related to the Kicad libraries and in fact are not even near the same folder.
My personal libraries contain the special sensors, devices, etc and are located under the My Documents library in windows. This way they get backed up whenever I backup my other documents.
They are preceded by my 1st initial and an underline. Makes picking them out very easy.
i.e. j_sensors.kicad_sym