New boxed set release

I have a boxed set of the CBSO/Simon Rattle/Sibelius symphonies. The tracks are exactly the same as in this release group: but it is the UK release on the EMI label, not the Warner EU release, and has different artwork etc. Each of the individual discs is in MB - eg but not this particular boxed set - as far as I can see from

So it seems I need to create a new release and link it in somehow, but I’m a bit new at this game and unsure about what is the correct sequence of operations. Do I add a new release from within the existing release group and then link the other discs into it? Will this get all the tracks listed exactly as they are in the other boxed set? I’m a bit nervous about doing it and getting it horribly wrong!

Add a release from the sidebar of the existing release group page (or just paste the release group URL into the “Release Group” field).

Then, on the “Release Duplicates” tab, you can choose to base the new release on the existing one.

Check the tracklist to make sure everything is actually the same.

I did that but the tracklist is not copied - see Release group “The Complete Symphonies” by Sibelius; City of Birmingham Symphony Orchestra, Simon Rattle - MusicBrainz
What do I do now?

On the Tracklist tab, did you expand all the CDs to see the tracks?

You should be able to add the discs one by one with the “Add medium” button on the tracklist tab, if a release duplicate attempt doesn’t work.

er no.
but this worked…

Now should I link the individual EMI releases to the Boxed Set via “included in”? I took a look at doing this, but it only links to the release group. The release group is named (and pictured) based on the previously entered set which was a later re-release (2013) of the one I have entered (1991). The individual EMI releases are all the 1991 and prior releases. Do I now need to change the release group details?