I am using Windows 10 Home 64-bit version.
Since I was having problems with KiCad 5.1.6 and had received a tip here in forum that version 5.1.7 could solve the problem I rushed to install the latter. I deinstalled the Version 5.1.6 without caring much about my self-created symbols in the KiCad global lib.
I only realised my folly only after the clean installation of version 5.1.7 was complete and actually I was expecting to loose all my symbols. However to my great surprise I found that KiCad lib still had my self-created symbols.
Probably, during deinstallation of the older version, the KiCad symbol lib is not deleted and the new version intallation - if it detects an already existing symbol lib - does not overwrite it. This is of course a wild assumption and may not be true, you would know it better.
But anyway for today, all’s well that ends well
Thanks for your help anyway, I’ll keep your suggestion about custom libraries in mind.