For anyone else who stumbles across this thread: when modifying the superwhisper toggle settings, hit spacebar then control, instead of control then spacebar. Also, it turns out that Control + Space is the default shortcut for switching keyboard input sources (at least on macOS Sequoia 15.3.1), make sure to disable that by going to System Settings → Keyboard → Keyboard Shortcuts →Input Sources.
Control space
For anyone else who stumbles across this thread: when modifying the superwhisper toggle settings, hit spacebar then control, instead of control then spacebar. Also, it turns out that Control + Space is the default shortcut for switching keyboard input sources (at least on macOS Sequoia 15.3.1), make sure to disable that by going to System Settings → Keyboard → Keyboard Shortcuts → Input Sources.