where do i find my key after sideloading?
The key is on the itch.io purchase page which comes up immediately after purchasing. It can always be recovered through your purchase email or itch.io account.
Please refer this support page for specifics: https://itch.io/docs/buying/already-bought
The key used to anonymously activate Quest Game Tuner will display on itch.io as an "External Key". You may need to click a button to claim it.