Libre Office does allow customising shortcuts. I got peeved when Ctrl+Plus (or Ctrl+Shift+=) is not available to add rows or columns, but found that it is very much possible to add it within Libre Office Calc itself.

From my notes (MD):-

- The shortcut can be reassigned under Tools > Customise > keyboard

- Add Ctrl+Shift+= (Equals to not Plus) too

- Select category All commands, scroll down there are 2 Insert Cells

- Hover mouse over. It shows the Uno command. Pick the one with `.uno:InsertCell`

- Under Shrtcut Keys select Shift+Ctrl+= and click on Assign