I have a custom app (Dimmer Button Controller) meant to simulate multi-taps on devices that do not natively support this, with my intent being to emulate the Hue Dimmer (where presses 1-5 of the "On" button can cycle through up to the same number of scenes) on Hubitat with arbitrary button devices, like a Pico (or even a Hue Dimmer, which doesn't actually send different events for multiple presses; this is apparently implemented in software on Hue, too). However, that might be overkill for your situation.
I'd suggest following the advice above first to make sure your dimmer doesn't actually natively support double taps. This is a poorly documented "hidden" feature on a lot of GE switches/dimmers, but (due to that fact) I'm not sure how long it's been around. There are some community drivers for the Plus versions, but I'm not sure if the "classic" one support this. (Though if you do have one of those, I might recommend replacing it when you can--most modern dimmers natively support this feature, and you'd get the benefits of Plus like better range and bandwith, through-the-mesh pairing, and it's likely yours don't support instant status reports from physical changes, which these would, so you'd be able to fully avoid polling and the problems that may arise from that.)
If yours doesn't, this would be pretty easy to do with Rule Machine with a "Button Device" (not "Button" trigger, though if this is the oly button number you want to control, the difference would be minimal). For your button 1 pushed actions, something like this would work:
IF (Private Boolean is True) THEN
On: Dimmer
Set Private Boolean False
Cancel Delayed Actions
ELSE
Set Dimmer to 100%
Set Private Boolean True
Set Private Boolean False --> delayed 0:00:05 (cancelable)
END-IF
This would let you do two taps within 5 seconds (easily adjustable); the first would just turn it on, while the second would set it to 100%. I wouldn't really "double tap"--I'd start by giving it a second or two between taps and seeing how quickly you can go before it might cause problems (you can probably go lower, but I just wouldn't start there; with my custom app, I notice issues with some devices if I go faster than about 2-3 times per second). Using a local variable instead of Private Boolean (in a similar fashion) might make this a bit faster, but you might need to give both the rule and your Z-Wave device some time to finish doing their thing.