ok: now I have a file sitting at /home/myname/.local/share/applications/Keyboard-toggle.desktop. The file name is "Keyboard-toggle.desktop".
a) it doesn't show in More Applications > Monitoring;
b) the procedure " PCLinuxOS Control Center. Hardware in the left pane, Set up the keyboard layout in the right panel, etc" doesn't lead me anywhere: once I add Arabic, US appears at the language switcher and replaces GB. Alt-Shift works (as it worked before, hence my previous doubt);
c) when I go to system, the localization windows show that my locale is GB...
d) if I re-set the keyboard language to GB, alt-shift (or the switcher on the taskbar) stops working.
I tried re-booting at different stages, to no avail. The other post mentions a "On the e17 desktop, go to Settings > Settings Panel (...)" which I don't understand.
Am I doing something wrong?