Developer Tools not appearing

I’m just getting started with theming, but I seem to have an issue with the “Developer Tools” (to inspect elements) not functioning at all.
As I understand it, from seeing some screenshots, the dev tools should be similar to the Firefox WebDev tools that appear at the foot of the window. But in my case, in Mailspring, nothing happens & no tools appear.

I am using Linux Manjaro & Mailspring is a Pamac installation via the AUR. v1.9.2-2

OK, it turns out there was an update to v1.10.3-1 but I had AUR updates off.
Once I updated the tools worked.