Why are the Ctrl-Shift-[number] shortcuts greyed-out?

NB this is on Linux (Mint 18.1). LibreOffice

In Writer, if you go Tools → Customise you find that Ctrl-Shift-0 to Ctrl-Shift-9 are greyed out.

Funnily enough I am aware that one of these is in fact a built-in shortcut in LO (I assume that it is not specific to Writer…):

Ctrl-Shift-0, which applies “Default Style”

  • NB this actually means, according to my experiments, that it removes any applied Paragraph style but not any applied Character style… to remove the Character style it is “Default Character”, for which I have set the shortcut Alt-Shift-0 in my system.

What about the others? i.e. Ctrl-Shift-1 to Ctrl-Shift-9: do they do something? If not, why can’t I assign them?

Ctrl-Shift-1 to Ctrl-Shift-9: do they do something?

Why not press and see?

Sigh. Mightn’t you just have assumed I did press them … and that nothing noticeable happens?

In Windows 10 they’re free to use, but some keys are grayed out, like F10, Ctrl+F4, all of which are predefined in the operating system. So maybe Ctrl+Shift+1-9 are predefined shortcuts in your Linux distro.

Oh, are they? In W10 I mean… a quick google, and the reference doc I have to Linux shortcuts doesn’t reveal anything… I’d better post that on a Linux forum, though. Thanks.