While it's not possible to achieve that through Google Groups web interface, because it is by design, you can do it if use your Gmail to keep up with the group. You can setup your group to receive e-mail on every post and the by replying to that mail and changing the subject, will force the group to create a new post. So in both places you can see your threads correctly.

Also it's a good idea to create a special filter for it to Skip inbox for example.

I figured it out.

1. Go to https://groups.google.com/ If you use the old interface for Google Groups click the button "Switch to the new groups". It should sit in the lower right corner of the browser window. If you cannot find it, visit https://groups.google.com/d/?fromgroups Now set the new interface as default.

2. Try going to https://groups.google.com/ You should now see only the new interface. It will redirect you to https://groups.google.com/forum/?fromgroups#!overview

3. From here, click on the "Browse all" link. It will take you to https://groups.google.com/forum/?fromgroups#!browse Here you should see the group categories as you're used to with the classic Google Groups interface. Only here you will not see any icons for the categories, just simple blue links. I guess it fits better with the new interface design.

Now here's what happens if I click on the "My groups" link from here.

1. Click on "My groups" link on the left. It will take me to https://groups.google.com/forum/?fromgroups#!myforums It says "You also belong to groups in 1 other organization. show; View 1 group at googleproductforums.com"

2. Click on the link. It takes me to https://productforums.google.com/forum/#!myforums "Google Product Forums (59 subgroups)"

3. Click on the "Home" link on the left. It takes me to https://productforums.google.com/forum/#!overview

4. Click on "Browse all" button. It takes me to https://productforums.google.com/forum/#!forumsearch/ and it shows all the subgroups... I think.

So my conclusion is that https://productforums.google.com and https://groups.google.com/ are not the same thing. Go figure! The former uses Google Groups service, but it is a separate Google website. It has no browsing of groups (subgroups actually) by category, since there are no more than 59 subgroups to Google Product Forums or 277 subgroups in total.

The same is true even if you use the classic Google Groups interface. So just make sure you are actually at https://groups.google.com/ and not some random website URL that only uses the Google Groups service and is not actually "the" Google Groups [website].