TL;DR: I cannot seem to get the idle_inhibitor module in waybar to appear in the waybar panel. Tried on two different hardware platforms, same result - won’t show up.
Details:
CONTEXT: I’ve successfully got waybar running under sway with a variety of modules. I’ve nicely styled css according to taste. Everything works beautifully, including hovers, on-clicks, etc.
ISSUE: But for some reason, having included various sample code examples shown on the idle_inhibitor wiki and adding the "idle_inhibitor", entry to the modules section (tried modules-left and modules-right), logging out and back in again to sway, the inhibitor item never appears in the waybar.
I’ve carefully compared the syntax of the idle_inhibitor entries to other waybar modules. They certainly look to be consistent and clean.
FYI, I have the following line in my sway config to produce a 10 minute screen blank. I thought perhaps this may be complicating matters? …
exec swayidle -w timeout 600 'swaymsg "output * power off"' resume 'swaymsg "output * power on"'
But when I remove this line and restart, it makes no difference … still no sign of the idle_inhibitor widget in the waybar. 
Any ideas as to how to activate the inhibitor … and get it to become visible in waybar?
UPDATE: I think I’m on to something…
When I remove the following line (originally copied from the wiki example code) …
"format": "{status} {timeleft}/{timeout}",
I finally get an “activated/deactivated” button to appear in the waybar. And clicking on it toggles its state, so it appears to be working.
There may be something funky about this line. Will report back any further insights. 
UPDATE #2:
Yeah, there’s definitely something glitchy about this line from the example code appearing on the module’s wiki:
"format": "{status} {timeleft}/{timeout}",
When I delete it, the module appears (and likely functions properly). If anyone else is struggling with this, perhaps this thread will be of help in your own sleuthing. 
I did some testing, and found that your example is one of the few that doesn’t display anything. For example, I tried this:
"idle_inhibitor": {
"format": "{icon} {status}",
"format-icons": {
"activated": "",
"deactivated": ""
},
"timeout": 5.0,
"wait-for-activity": true
},
and it works as expected. When adding {timeleft}/{timeout}, it doesn’t. Very strange…
Indeed. I’m guessing it’s some kind of syntax interpretation quirk. Perhaps use of spaces, slashes, whatever.
Not a big deal as there are countless ways to tweak things to taste (as I’ve managed to finally do).
But if others in the future are splashing around wondering why their waybar idle_inhibitor module doesn’t appear using this sample code from the wiki, hopefully this exchange will be of help.
Would’ve saved me some frustration. 
@ajgringo619 EDIT: BTW, I decided to use the single icon by itself when deactivated, but added descriptive text to the activated icon line above (using the format icons section).
Don’t need to take up so much real estate when it’s not active … but don’t want to lose sight of the fact that sleep is prevented while it’s activated. Also changed the color to red when it’s activated - in the css style file.

