Sorry if it's just my blindness. I cannot see a good way to access the list of topic that I started on the forum.

The top menu offers just 'Forum replies'. But that only displays my replies from the last 24hrs. When accessed 'Community->All forums' I only got access to the topics I participated in.

I tried to find that in 'My Profile', but I was unable to.

In my view it could be a very useful option. What do you think?

You didn't, the forum software doesn't have a list of your topics. :(

Ironically, it’s the only part of the website which actually works!

Yeah, a list of participated topics would be a pretty nice thing. But given that many of us can't even reach the recent posts anymore, I doubt they'd be able to handle the hell archive.

It used to be that new threads weren't listed in the "Topics I've participated in" section, but they seem to have relatvely recently (last few months or so, maybe?) been added, now (unless I am imagining things). If only they would sort the list by last modified date rather than first post date, that would be ideal (yes, I added a wishlist entry for that years ago, but nobody voted for it).

The most you can do is have everything you did bookmarked, then search for your username with ctrl F.

But since bookmarking then ctrl F-ing is the solution for most problems in the forum, you may end in a situation like mine where you're constantly nearing the 2500 bookmarked posts, and when you get to that point, the main pages of the general forum simply refuse to load.

The forum software does not offer a list of topics you've created.  However, if you're patient enough, you can find them in your activity feed.  To spot them, you'll need to browse through several pages and search for your username using the web browser's built-in search.  Personally, I bookmark or pin any interesting topics that I follow or in which I participate.

Probably the best you can do is going to the "All forums" page and keep clicking "show more" button in the "Topics I've participated in" section until you find what you are looking for.

But no, listing threads started by you is another basic functionality the GOG forums don't have.