For now, you can look it up in the radial menu but even that doesn't show it correctly all the time. If I turn the attached machine on/off with the Keyboard (B), the radial menu is sometimes not updated.
As a workaround you can put the On/Off action of your machine into a quickslot (hover over the action in the radial menu, press 'F' and assign a Quickslot number).
The quickslot icon will turn green if turned on.
Die Kunst der Programmierung besteht darin, eine leere Textdatei mit Bugs zu befüllen System: i5-3570k | AsRock Z77 Pro4 | 16GB DDR3 | Nvidia RTX 2060 Super | OS: Gentoo Linux | DE: awesomewm