How to add a button to the Home tab in the Tabbed UI of Calc?

I can add the “Split Cells” command using a “Target” of “Standard” but it only shows when I’m not using the new Tabbed User Interface. How do I add this command to the “Home” tab so that it resides right next to the “Merge Cells” command? I don’t see a “Target” of “Home”. Thanks

Which OS- and LO-Version do you use?

Win10 and LibreOffice 6.2.0.3 x64