Hubitat does not have a built-in driver for the LZW31-SN (Red Series Dimmer), so you'll have to use a third-party driver like Inovelli's own for that. To set the notification LED from RM, the driver will need to expose a command for that, as you must know since you asked. However, last time I used Inovelli's own, they didn't--the child devices were the only option. I have my own that does provide custom commands if you wanted to try that out. It also has the option to create child devices for the LED itself. That is optional, and the difference from Inovelli's own drivers is that this would be a child device for the notification LED (and the default "on" and "off" LED, though those support fewer features) that expose the LED as more or less just an RGB bulb that you can manipulate directly and turn "on" to activate the notification--no need to pre-define child devices for notifications (I was also not a fan of that). But you don't need to do that, as you could also just use the custom command on the parent device.
For the LZW30-SN (Red Series Switch), Hubitat does have a driver built in ("Inovelli Z-Wave Smart Scene Switch S2"). That one, like mine and whatever one you've apparently also seen, does indeed have the setIndicator command. It has fewer features than Inovelli's own driver (which again doesn't implement a command like this) or my own (I haven't documented its existence yet but I do indeed have one for the LZW30-SN, too). Notably, Hubitat's built-in drivers all stop at "double tapped," so you'll lose out on the third, fourth, and fifth taps up or down on the paddle as events you can respond to. (Speaking of these, I'm also not a fan of what button-related events Inovelli chose to generate here. A tap up is "1 pushed," but a tap down is..."1 held"? On mine, "1 pushed" is a tap up and "1 held" is...wait for it...a hold of the "up" paddle. The tradeoff is that you need to do some arithmetic: the top paddle taps are buttons 1, 3, 5, 7, 9; the bottom paddle taps are buttons 2, 4, 6, 8, and 10; 1 and 2 support held and released as their logical real-world events; button 11 is the config button.)
Also, if you haven't seen this thread on the Inovelli forums, here's an easy way to calculate the value you'd need to set this parameter manually: Visual Notification LED Calculator Updated for LZW31-SN Dimmer - Digital Lounge - Inovelli Community.
As to how to actually use these commands, no matter what driver you use, in RM: they aren't standard commands, so none of RM's built-in actions can run them directly. What you need to do is use the "Run Custom Action" feature, which is an action you can choose, then fill in whatever else you want:
(If you haven't used this before, the "Select capability..." option will work if you choose any capability the switch/dimmer supports. It's just a way to get RM to present a list of devices to you. I chose "Switch" because both the switch and dimmer would support this, but as long as whatever you choose gets the device you want in the list, it doesn't matter; RM will have access to all its commands regardless.)
Hope this helps!
But because it's all crammed into one parameter, you'll have to do some work to get there. (The driver I wrote, above, does make this easier by treating the notification LED as an RGB bulb where you can set all of these separately. You'd need to do a 
