Put a link to the exe somewhere (e.g. the start-up folder in the start menu). Than edit the target to add the argument: C:\Users\[your_username]\AppData\Local

Put a link to the exe somewhere (e.g. the start-up folder in the start menu). Than edit the target to add the argument: C:\Users\[your_username]\AppData\Local\Programs\signal-desktop\Signal.exe --start-in-tray