I think I follow your set-up (wink.)
First, if memory serves me right – I think the “all off” functionality is “built-in” to Harmony. So, I don’t think you need to create your own activity for it? (e.g. look at your Harmony remote, and see the “OFF” button. That should indeed turn EVERYTHING “off.”) So, you don’t need to create your own/separate “off activity” within Harmony.
So, you just point your SmartThings off-switch to this Harmony button = easy peasy.
In your specific example, you would point your LRTV switch to the “Harmony off” button.
Second, I would name your virtual devices to be the same name you want to use for Alexa (minimize the number of translations along the way.) e.g. I would rename your switch from “LRTV” to be “Living Room TV.” This way, Alexa imports the exact name of the switch, and you can indeed just say “Alexa, turn off the Living Room TV” – and she will know exactly what you said.
Personally, I’d rename your “off” to be something more “global.” e.g. use the same/single command – to turn off the TV, the Xbox, whatever. This is why I named my off routine "Entertainment Center."
So, whether you are watching Xbox, or CableTV – you just say “Alexa, turn off the Entertainment Center” – and she will turn off WHATEVER is being used/watched.
Then, INCLUDE the “Entertainment Center” in ALL of your harmony enter/exit commands. Have it turn “on” the entertainment center when your “Watch activities” are run, and respectively have it turn OFF the Entertainment Center when you exit the activities. Remember: Harmony does it’s own “background math” to determine whether to really turn it off. If you are SWITCHING from one activity, to the next – Harmony compares the CURRENT state of the CURRENT activity, to the TARGET state of the NEXT activity. If both activities have the Entertainment Center “on” – then Harmony won’t turn it off, and back on. Instead, it will just leave it on as it makes the transition from CURRENT to NEXT.
Personally, I don’t need/use any “momentary switches,” because I want to see the current status of anything/everything, and turn devices on/off with specific intent. Momentary switches simply do a quickie on, and an automatic quickie-off, too. So, they never appear as “on” during subsequent status reviews. I prefer to only turn them off, when I REALLY want/see them as “off.”
e.g. when I turn on my TV/cable, I see ALL of the following switches/devices as "on:"
Entertainment Center, TV (set-top-box,) Soundbar, set-top-box.
Whereas, if we’re playing the Xbox, we’d see the following as "on:"
Entertainment Center, Xbox, Soundbar.
And, if we’re watching something from our PS media center, we see:
Entertainment Center, Computer, Soundbar.
If we’re streaming content from SmartTV Hulu:
Entertainment Center, Hulu, Soundbar.
So, if I’m away from home, and look at my SmartTiles dashboard, and I see:
Entertainment Center, Netflix, Soundbar
I know EXACTLY what’s on, and what it’s being used for. (e.g. my family/guests are watching something on Netflix.) Which means they are NOT playing Xbox, or watching satellite TV, etc.
It CAN initially be confusing!!! (agreed)
But, once you comprehend/understand it, it gets a little easier.
Extra credit brownie points:
Set-up other “modes” for your home, and then make sure all of your ST events are indeed running during the proper modes. More importantly, that they AREN’T running during specific modes.
Example: I created a MODE called “All OFF.” NONE of my ST events/activities/scripts are allowed to run during “All OFF” mode. This allows me (with just one button press) to disable EVERYTHING – and go old-school. So, when we have guests who aren’t comfortable with all of the automation and such, I can just “flip a switch” to turn EVERYTHING off. Once the leave, I can just switch the mode back to “home” – and everything resumes business-as-usual.
I have another mode called “Visitors.” This mode just disables SOME of the routines. (e.g. the living room lights that automatically come on every morning, and my Jarvis/IronMan script that speaks the weather/surf conditions and such.) I don’t want to rudely wake-up my visitors with lights in their eyes at 7am, when they are trying to sleep-in on my sofa-sleeper. But, all of the OTHER routines throughout the home still work BAU (business as usual.) So, “Visitor” is just a limp-mode of sorts. Whereas, “All OFF” is indeed a complete disabler of ALL our SmartThigngs stuff.
I also find the All-OFF to be helpful when I’m trying to create/test new routines. e.g. test ONLY that new routine. So, it’s the ONLY routine that’s active during the All-OFF mode. Once I work out the kinks, I then switch it to the other/respective modes, and remove it from the All-OFF mode.