There is no official manual for the Vortex Race 3 75% mechanical keyboard I got recently, but the programming instructions from the POK3R user manual still apply almost exactly:

To program one of the layers 2-4 (the first one cannot be programmed) follow the following steps:

1. Choose the layer you want to program (Fn + <,>).
2. Enter the programming mode Fn + Right Ctrl. Spacebar right LED should lit steadily.
3. Press the key you want to program. Spacebar right LED flashing.
4. Press the keys you want and then press Pn. Spacebar right LED lit steadily again.
5. Repeat to program other keys.
6. Press Fn + Right Ctrl to exit programming mode. Spacebar right LED off.

Although there is already a macOS layer, at minimum you probably would want to map these combinations as well, to benefit from the extra Home and End keys:

⌘ + Left  (CMD + Left) → Home 
⌘ + Right (CMD + Left) → End

Notes

• Every key can program up to 32 key strokes.
• To reset a programmed layer, press and hold FN + R. Spacebar left LED will flash for around 5 seconds, then the layer will be restored to default.