the default hotkeys are 1-10 or f1-f10
From Fox Lee:
"I use a really simple AutoHotkey script to send my numpad key presses to Gazō Tuber even when I have some other window in focus. If you're interested"
https://drive.google.com/file/d/1vyrpqycn1ZQgIqAvkrqA-RRAd5mCVEv5/view