What would be the best way to assign a hot key or button on a deck to flip the phase in FabFilter ProQ?

Hello Gary
This should work to toggle the phase button. Should work on proQ 2 or 3.
Its set for the extra large size

const firstFabFilter = sf.ui.proTools.children.whoseRole.is("AXWindow").whoseTitle.startsWith("Plug-in: FabFilter Pro-Q").first

const menuPos = { "x": 990, "y": 810 };
const phaseBtnPos = { "x": 990, "y": 787 }

if (firstFabFilter.exists) {

    firstFabFilter.mouseClickElement({ relativePosition: menuPos });

    sf.wait({ intervalMs: 200 });

    firstFabFilter.mouseClickElement({ relativePosition: phaseBtnPos });

    sf.wait({ intervalMs: 200 });

    firstFabFilter.mouseClickElement({ relativePosition: menuPos });
};

If you need to adapt the script, here's Kitch explaining the process.
How to use "Mouse Click Relative to UI Element" to simulate mouse clicks in Pro Tools.

Thanks Samuel! That's working but it's clicking the AutoGain button just to the right of the ø button. thanks for the link to Kitch's video -- I think I can probably use that to tweak your script for Large window size and the ø button instead of AGC. thanks!