The Plover key (top right key on the left half) also sends my Plover ‘toggle’ chord (SH-FT) when pressed, as well as toggling the steno layer, so you can toggle between steno and typing modes with a single keypress.
If you want to use this feature, you'll need to add:
"SH-FT": "{PLOVER:TOGGLE}"
to your Plover dictionary.