I don't think there are too many places outside General Discussion you can do this until you upload a project.

Once you upload a project (even if it's in a very early state)- you've then got something you can put in the 'Developer Logs' section (at the top of the page) and the Devlogs forum- which are two separate things. There's also the devlog section of your project which- I think- is something else altogether. 

I won't lie... I get a bit confused about these XD

These sections mainly feature as shop windows for players so, you might not get too much actual gamedev discussion, if that's what you want, but they're good places to signpost people to if there's anything you want to talk about.

Hope this is at least vaguely helpful!