iw dev <interface> station dump will show every metric about the connection, including the signal strength and average signal strength.

It won't show it as an ascii graphic as with nmcli, but it shouldn't be hard to create a wrapper script to grep that info and convert it to a simplified output if you're willing to put in the effort of understanding the dBm numbers.

E.g. -10 dBm is the maximum possible and -100 dBm is the minimum (for the 802.11 spec), but the scale is logarithmic so -90 dBm is 10x stronger than the absolute minimum needed for connectivity, and I can only get ~-20 dBm with my laptop touching the AP.

Basically my point is that the good ol' "bars" method of demonstrating connection strength was arbitrarily decided and isn't closely tied to connection quality. This way you get to decide what numbers you want to equate to a 100% connection.

Ah alright. 😂 Thanks for pointing out the mistake. Appreciate it.

Because the machine could be headless so it can't display the applet to click on

It's as other said, headless. Sometimes I only need to check if the signal strength is alright, as I use that machine as servers and host several service on it.