itch.io

After you press play you can find the infinimoes.js file under index.html in the sources tab (I use chrome but I assume it has a similar name) then in it you can put breakpoint by clicking on the left side of the the line (put it somewhere where FS is used) then refresh the page and after the breakpoint was reached you should have access (just continue after it was reached)

Thanks for the info, in my case it worked fine without changing.
Also, which part in my method didn't work for you?

if anyone played the demo and then bought the game you can keep the demo save using the following js code (you need to first use a breakpoint in their js code)

save = FS.readFile("/user_data/cdata/werxzy_infinimoes_demo.p8d.txt")

var string = new TextDecoder().decode(save);

then copy the string content to the save game at 

%appdata%\Roaming\pico-8\cdata

or wherever it is in linux/mac