[Beta Designer] Improvements to the Properties panel

[stefano.menci]

@hugetim

I’d like only one of the major sections (Add Components, Properties, Components) to be open at a time. Hey, why not make them tabs?

I agree. Whether they are tabs or not, it’s important that it’s clear which one is open. That’s what I meant here:

@stefano.menci

It would be better to only open the panel that I explicitly want to open.

But using tabs there is one further advantage: all the tab names would be at the top, while keeping collapsible sections would push some of the names down.