Hello @catbill,
+1 for interesting find.
First i tried pressing Shift+Backspace in my Writer document, and like you said, it does exactly the same as pressing only Backspace ( without Shift ), that is, it deletes the selection or the character to the left.
In my Keyboard Shortcuts tab in “Tools : Customize...”, there is also a Shortcut defined for Shift+Backspace, and its description indeed reads: “Shift+Backspace” … Not much info there...
Then i searched for the Shortcut Key “Shift+Backspace” in the Help file Shortcut Keys for LibreOffice Writer, but unfortunately no Shortcut Key for “Shift+Backspace” is listed there.
Yet i saw that there exists a special UNO Dispatch command called .uno:ShiftBackspace with the corresponding identifier FN_SHIFT_BACKSPACE in the source code, so the Shortcut Key must be relevant too.
Searching in OpenGrok it revealed this page.
Interpreting this code on first sight, it appears to me that the command FN_SHIFT_BACKSPACE does exactly the same as the command FN_BACKSPACE listed one case up, but without taking an eventual Numbering/Outline level into consideration.
I guess that way one could hold Shift+Backspace inside a Numbered List, then it will keep on deleting until the number, then it stops.
Hope this helps,
lib
