itch.io

For Windows:

1. navigate to C:\Users\[user name]\AppData\LocalLow\Sebastian Lague\Digital Logic Sim\SaveData\[saved project]  and delete the unwanted .txt file.
2. navigate to C:\Users\[user name]\AppData\LocalLow\Sebastian Lague\Digital Logic Sim\SaveData\[saved project]\WireLayout and delete the unwanted .txt file.

The path on your computer may be slightly different. it may also be in roaming instead of local. I don't know the difference. All I know is this is what worked for me.