Npp UI Spy plugin
That’s a great place to get the menuCmdId codes like 42024 that were mentioned – those are the command ID values for all the Notepad++ menu entries. (The type="2" codes, as described in the config files: macros section of the Online User Manual.)
because Scintilla commands are numerous
Scintilla commands are not included in Npp UI Spy plugin, since they aren’t UI menu commands, so no matter how numerous they are, you will find 0 of them in the Npp UI Spy plugin.
However, you can find the Scintilla numbers enumerated and briefly described in the Scintilla.iface which linked from that same section of the Online User Manual. And the Manual also links to the canonical sources for the menuCmdId values.