Thanks for the answer.
Nevertheless, using Calc LO 6.4, the first PDF command (not the second) does the same as the button Export directly as PDF: it takes you directly to the save dialog. Another “feature” of this command is that (at least in calc) it export the sheet, not the selected cells
Instead, if you use the first PDF command it takes you to the export settings dialog (as in File>Export as pdf). It’s a big difference when you are exporting repeatedly several files because of the extra steps you have in the “export as pdf” command and the fact that the default setting there is to export only selected cells.
At least, the command names in the Customize>keyboard menu should be corrected to match the label of the button and the File menu entry correspondingly so you can realize that each one refers to the same function.
I agree it would be good to have a shortcut for “Exort directly…” by default.