I'm sure there has been plenty of players who have experienced this before, where you accidentally tap the 'instantly finish' now button and spend donuts out of error. With the latest update it's been trickier for me.
For example, today I was starting a training unit and the mobile app loads things a bit slower for me since the new interface has launched. Sometimes I'll tap a button and it appears it hasn't been tapped, so I figure the icons are smaller to tap, so I'll tap again. The issue is sometimes I actually tapped it and it is delayed in my view, then I'll end up wasting a donut. A donut here or there, sure it certainly adds up especially when a donut sale isn't around the corner. I used mobile as an example, but have done my share of unplanned clicks on my PC.
My suggestion is to have a 'donut safe mode', that allows us to disable using donuts when ticked on, and when ticked off, donuts are freely spent how they normally are. Maybe a pop up that says you have donut safe mode if you forget it's ticked on... etc.
Would definitely save some donuts when the screen is slow to respond, or any other time we tap slightly too close to the finish button.
Not sure if this has been suggested before, but would really like a feature like this!