Hi all,
I'm also interested in this, and when I tested DSpace 8 I think I tried something like the approach proposed by Tim and it didn't work (and as a consequence, I postponed the upgrade).
I'm talking from memory, but the main problem is that the "initial" active tab in the communities and collections page is selected based on the last segment of the community URL (and not the order of appearance).
In DSpace 7, the subcommunities and collections tab was rendered when the base URL for the community was navigated, e.g.:
But in DSpace 8, the URL for the subcommunities and collections has the "/subcom-cols" suffix, e.g.:
Thus, to activate the subcommunities and collections tab all links to communities and collections in DSpace would have to include the "/subcom-cols" suffix (which doesn't seem an easy fix to make).
When I found the above issue I gave up since I wasn't able to find a satisfactory and straightforward solution.
Please, let me know if I'm mistaken. I'll be happy to be :-)
Abel