Hi I Had a good look at all of the above.
Using the the generateTicks looks the closest, but this seems to just be for the bottom most header?
Ie if I add a colsole.log...
timeAxis : {
continuous : false,
generateTicks(start, end, unit, increment) {
const ticks = [];
console.log(unit); // <-- added by me
while (start < end) {
...
it only even seems to be called for the bottom axis...

- bottomaxis.png (17.32 KiB) Viewed 57 times
I was more after having an "upper" header that can group different number of hours together.
Eg as below, shift 1 has less hours than shift 2. Note in my case the times WILL be continuous

- bottomaxis.png (17.32 KiB) Viewed 57 times
Is this at all possible?
Thanks in advance