Task properties dialog keeps changing. We discarded our home-grown bogus system of collapsable and hideable panes that had appeared in M2 and implemented it on top of Flexdock library. It works fine, and now you have some freedom in task properties layout. For instance, it is easy to arrange them like this:
Just drag any tab and drop it where you want it to be. While dragging, flexdock outlines possible drop targets, and creating necessary layout is really easy.
And yes, task dependencies panel is back. It looks similar to resources panel and autocompletion also works: