I've currently updated the plugin to version 1.1.2 and also updated the sample project for microtransactions. As for the issue with pressing Esc triggering the closure of the Steam Overlay, I've heard that this is a problem with Steam itself. I've also tested the microtransaction functionality in a game called 'KUUKIYOMI: Consider It,' and it seems to have the same issue with Esc.
Thank you for the information.
'KUUKIYOMI' was developed as Unity, but it had the same problem. I knew the Steam overlay would close if I pressed ESC, but I thought it was because of the RPG MAKER MZ or plugin that the overlay wouldn't open again.
I don't know if Valve will solve this problem. There are a lot of games that don't have problems. I hope this problem will be solved someday. Have a nice day.