How to map the extra 4 keys from rev4 using QMK ?

[luc-vocab]

I am looking at the merge request to add crkbd v4 to QMK here : qmk/qmk_firmware#24084
but it's not clear to me how the extra 4 keys can be mapped, how is it possible using the LAYOUT_split_3x6_3 macro ? Is there a sample somewhere ?

[luc-vocab]

For the layout macro, we have to use LAYOUT_split_3x6_3_ex2
I received a pre-assembled crkbd 4.1 which works fine with the default firmware from https://github.com/foostan/crkbd/blob/main/docs/firmware/rev4/firmware_en.md.
however when I build my own firmware with the above qmk pull request using qmk compile -kb crkbd/rev4 -km via, only one half works at a time. Does anyone have any suggestions on troubleshooting steps I could try ?

[foostan]

Have you checked https://github.com/foostan/kbd_firmware?

[luc-vocab]

@foostan I am trying right now, will report back very soon

[luc-vocab]

I can confirm it works when following the instructions here: https://github.com/foostan/kbd_firmware, thank you.