This readds the collapsible feature which was accidentally removed in f0d7e06241585543bd49699face4ac0ff76cc662.
This is also missing in NIAC PR1303, so it should probablye be merged in nyaml2nxdl-migration branch and the PR.
We should also readd the little arrows which point to the super concepts before merging this. So I agree @mkuehbach that we should go through and check what is in PR1303 and what we need to add there.
This readds the collapsible feature which was accidentally removed in f0d7e06241585543bd49699face4ac0ff76cc662. This is also missing in NIAC PR1303, so it should probablye be merged in nyaml2nxdl-migration branch and the PR.