Hi,
I'm working on a patch in Okular, based on the following task:
https://phabricator.kde.org/T8553
Basically, it adds a button to expand and collapse all elements, you can see it here:
https://phabricator.kde.org/D18358
I'm definitely not the person to go when it goes to design, but I think it would be like this?
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRDCqeC3TpSWC9Sp0lWMGj61BNLLeLbThl32ybmxBC-3wOpp_If

Thanks for the help.

-- João Netto