Some Calibre configuration disappeared
 

Hi all - today I opened my Calibre after about 4 days inactivity and was surprised how the title page changed. The Main toolbar is different - installed plugins disappeared, when I click Choose Library I can only see the last library, the other libraries are not available (there is nothing wrong with those libraries, they are still where they used to be on my HDs). Some other entries on the Main toolbar are gone. Actually my plugins exist, if I go to Preferences -> Toolbars and menus, I would be able to put them back to the Main toolbar. Also my Virtual library config is not displayed on the title page, but it exists and can be put back. Also the libray lines on the title page have a different, bigger line height.
I could probably configure everything back. Also I have 3-4 month old backup of Calibre but if I use it I would obviously loose my latest setting...
So before I will proceed with fixing it, I would like to ask you - why this happen and is there any easy way to get it all back?
For about 3 months now I'm using Windows 10 to which I successfully transplanted my Calibre from my old Windows 7 system.
Thanks.

Something walk all over the Calibre configuration folder
OR
You logged on as a different user ( config, PI are per user)

Thanks theducks. I'm logged correctly, so something must've walk all over... I don't get it how that is possible. Who was that? MS update?

What is the name of the file where this configuration is stored or where would I get those details, please?

You can acces the configuration folder from Preferences->Miscellaneous

Thanks kovidgoyal - I know that, but where exactly are stored the settings of the main screen which I set in preferences, e.g. changes to the Main toolbar?
Or are they in the metadata_db_prefs_backup.json or metadata_pre_restore.db files related to the currently open library? Or why my other libraries are not listed in Choose Library? (I can re-establish them again, but I would like to see if I can possibly fix it in a config file...)
I would like to see what happen to my current calibre config files as compared with my 3 months old files on my old win 7 system which I never used since.

It varies, some settings are per library some are global, etc. IIRS toolbar settings are in gui.json

Thanks kovidgoyal