Bozhidar Batsov has a quick post on a recent enhancement to Emacs Flymake. The TL;DR is that you can arrange for Flymake to append a diagnostic at the end of any line with a problem. It’s a quick way of seeing what the problem is and maybe fixing it without a lot of extra work.
As Batsov (and the documentation) says, that can get a little noisy so (of course) Emacs gives you a setting to control how much information is displayed. Take a look at Batsov’s post for the details.
I’ve never warmed up to Flymake but lots of people, I know, love it. If you’re one of those people, be sure to take a look at Batsov’s post. Everything is controlled by a single variable so it’s easy to try out the various options.
This feature is available only with Emacs 30 and later. Getting it may be a good reason to upgrade if you haven’t already.