frameSync() currently syncs to UTC hours. Yet, no markets (except Japan) are in UTC.

Would be very helpful if frameSync() works off hours in the selected BarZone and/or AssetMarketZone.

Thank you.

Or just write your own custom frame synchronizer. It's pretty simple, actually. Refer to the frameAlign example for inspiration:
https://zorro-trader.com/manual/en/tips.htm

Given enough time, I can write my own custom backtester. Do you mean to say that asking for frameSync() to work in some practically useful timezone is suuuch a narrow use-case/special request that it is to be left to be programmed by the user??