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@Gordon
As other have said, the Pico's 'peak' power consumption is really just too much for a standard CR2032. You could use a supercapacitor in parallel if you wanted, and that would make things work ok.
The Pico's processor will run down to around 2v, so the voltage isn't too much of an issue even with the regulator's ~0.3v voltage drop. It's just the stuff you want to connect the Pico to that might complain!
Do you have to use a Pico? The MDBT42 Breakout would happily run off a coin cell for quite a while.
I've actually tried these and they work great with the Pico - but as @allObjects says you don't get much capacity out of them