It looks like the wrench follows the same logic as the “pagination widget” - it doesn’t display for topics with only one post. That makes it impossible to do things like “set topic timer”, or “make unlisted” etc. when on a mobile device.
Repro: as an admin, make a PM to yourself. There’s no wrench
I removed it intentionally because there was no good place to display it anymore. Normally it would appear at the bottom - but at that point why not use the drop down that’s right there?
I went in to change this and realized just how different the drop down was from the admin menu! Instead what I think is a decent compromise is to not hide the progress bar on mobile topics, even if they’re short. That way, there is a decent looking place for the wrench.
The downside is you’ll see 1 / 1 topics but on a small screen it’s not so bad since you probably have to scroll to get to the bottom of the post anyway.