Refer also to the lists of shortcut keys for LibreOffice Calc and LibreOffice in general.
In a text box that has a button to minimize the dialog, press F2 to enter the cell selection mode. Select any number of cells, then press F2 again to show the dialog.
In the cell selection mode, you can use the common navigation keys to select cells.
You can use the keyboard in Outline:
Press F6 or Shift+F6 until the vertical or horizontal outline window has the focus.
Tab - cycle through all visible buttons from top to bottom or from left to right.
Shift+Tab - cycle through all visible buttons in the opposite direction.
Command+1 to Command+8Ctrl+1 to Ctrl+8 - show all levels up to the specified number; hide all higher levels.
Use + or - to show or hide the focused outline group.
Press Enter to activate the focused button.
Use Up, Down, Left, or Right arrow to cycle through all buttons in the current level.
Choose View - Toolbars - Drawing to open the Drawing toolbar.
Press F6 until the Drawing toolbar is selected.
If the selection tool is active, press CommandCtrl+Enter. This selects the first drawing object or graphic in the sheet.
Now you can use Tab to select the next drawing object or graphic and Shift+Tab to select the previous one.