Feature Request: Per-key Dual-Function Key timeout

[BlaiseRideout]

Is your feature request related to a problem? Please describe.
I use dual-function keys for modifiers on my home row (homerow mods). On my QMK keyboard, I have these configured to take less time to activate the hold function for things like shift that I need to be very responsive when typing quickly and have relatively low consequence if activated unintentionally, but to take more time for things like Control and the OS key since using these keys is usually much more intentional and accidentally activating those modifiers causes more problems. On my Dygma Defy, with the current limitation of a single global timeout, I have to accept the tradeoff of pressing shift taking too long, slowing down my overall typing speed, or pressing OS/Ctrl happening too quickly sometimes and accidentally pressing some keyboard shortcut when I'm actually just trying to type.

Describe the solution you'd like
Allow the "Dual-Function Key Hold timeout" setting to be customized on a per-key basis. Ex a shift modifier on hold on the D key that activates after holding the key for 150ms and a ctrl modifier on hold on the F key that activates after 200ms. It would be additionally convenient if in the layout editor UI, the timeouts could be configurable as an offset +/- from the global timeout instead of only as an absolute value.

Describe alternatives you've considered
No alternatives available really short of using a different keyboard or an OS-level solution instead.

Additional context
Similar to TAPPING_TERM_PER_KEY from QMK: https://github.com/qmk/qmk_firmware/blob/master/docs/tap_hold.md

[MiquelDygma]

Hi, Blaise

Sorry for tha late reply.

I've personally tried that feature on QMK, and it's really good. It's complicated for the layman but useful.

We're working on adding more configuration options for dual-function keys that will help with your problem, although it won't be per-key as you requested. At least not for now.

Thanks for the suggestion!