What have you tried? I'm not doubting your efforts. I think there's a very real wall people working to improve their working memory are bound to hit eventually, but I haven't explored things specifically designed to improve working memory.
I play video games, I play instruments, I write programs, and I have to imagine that all of it helps, but I haven't tried "brain training" or used tools marketed as improving working memory. I'm not even really sure what's on offer in that space, so if you've found some I'm curious to know about them.
Surprisingly, working in food service pushed my brain pretty hard for working memory. I managed to push myself from 3 items to 4, but it required constant effort to keep it there. The improvement would disappear after a week of not working.
I can’t think of any better test than trial by fire. Kind of like learning languages. Study all you want, theory won’t save you when it comes to practical application. :)
When it comes to programming, becoming familiar with your tools and learning to offload stuff to paper far exceeds anything else. If you know something well, you need less working memory to do it.
I play video games, I play instruments, I write programs, and I have to imagine that all of it helps, but I haven't tried "brain training" or used tools marketed as improving working memory. I'm not even really sure what's on offer in that space, so if you've found some I'm curious to know about them.