Thank you rich2005
.
it's OK and thanks to MareroQ.
I had the courage to go to the end of the 14min56 and I appreciate that, thanks to MareroQ, no need to open gtkcr with notePad++ to make the changes....
Being stubborn, I kept wondering why I couldn't copy and paste UI and gtkrc and found I could do it by going directly to D:\Gimp-2.10.22_Portable-32-64bit-Win\share\gimp\2.0\themes\Dark but not when I was viewing that folder from Edit/Preferences/Folders/Themes etc/...Weird but it won't keep me awake at night.