Emulator

While you can access both these features via the TAS Input plugin, it's much more convenient to have a given hotkey that you can use for these instead.

In other emulators, such as BizHawk, this is done by holding the Autohold key then press the button you wish to be held down, repeating the same action will release the key. With Autofire defaulting to automatically pressing a button every second frame. Including a "Clear" button to release all auto-held/fire keys automatically.