4.1.4
Chrome 68.0.3440.75, Windows 10 1803
Created a new project using the Vue CLI (webpack).
Installed Vuex.
Created a basic store. Added one property (array) and a mutation to alter it.
Committed a mutation, store does update (when logged), but the mutation doesn't show in dev tools.
I took screenshots of each step, which can be viewed here:
https://imgur.com/a/66ZCeSp
The mutation should show in dev tools. I know it used to, seems to have been a very recent update somewhere that has stopped this from working.
The mutation isn't showing in dev tools.
Be sure to check my screenshots here: https://imgur.com/a/66ZCeSp
You need to record the mutations:

Oh man, I didn't even think of this because it had always just been on. Thanks, I must have turned it off by accident somehow.
Jesus christ, I almost go crazy because of this
For googlers:
Another common thing I run into is something throwing an error. Sometimes I will have my vue devtools open without the console and wonder why my mutations aren't showing up. Nothing appears broken because with Vuex your state transitions from valid state to valid state. Check your console!
For me, nothing is showing when changing the route. My devtools doesn't can to show up anything, like it had lost the state completely, or get the state unregistered.
Most helpful comment
You need to record the mutations: