The synchronization with properties editor has just been added to master.
I am not a fan of the synchronization based the edge shared between Outliner and Properties Editor.
That removes freedom to build a workspace that makes sense.
Imagine that you have a very wide screen but you are lacking height.
So, you want 2 Properties Editors, next to each other but you also want an outliner that takes the entire height of screen.
You will have to place the outliner in the middle. But it would be easier to read a configuration where outliner is on one side and the 2 properties editor next to each other.
Most common case will be to want one Properties Editor synchronized with the outliner and another one, you want fixed.
For example, one fixed Properties editor dedicated to Active tool or Render Settings and another one for Object Properties in synchronization with Outliner.
In the case that you want to make one column with Outliner above a Properties Editor, you are forced to put another editor between Outliner and the non-synchronized Properties Editor.
And the smaller Properties Editor below Outliner can not be the one dedicated to Active Tool which is often the Tab with the less amount of Panels and Properties to display.
So, I propose to let user managing synchronization of Properties Editor while he is building a workspace by using context menu of properties editor.
Currently user just have to do a right click on Context line or empty space of Properties Editor to display right click menu.
This right click menu is almost empty. It just displays area sub-menu.
There could be an item with checkbox in this menu Sync with Outliner.
For the first time, in a decade, passed requesting a way to make a 2 column layout for Properties Editor, in order to see all properties : I think that you inspired me an elegant solution.
A snapping choice for scrollbar of Properties Editor, available in Properties Editor Context menu.
Currently, Properties Editor shows almost always panels at the top of the Editor.
Whatever was the scrolling you did in a tab with several opened panels, you lose it when you go to a tab with only one panel like Modifier stack.
That will be great to be able to snap scrollbar to bottom or center of editor.
3 choices like Top/Center/Bottom would be alignment options (similar to options for text alignment).
Using such solution for tabs with many properties like Render, Particles or Physics tab : that would become easy to build workspace with 3 columns of settings synchronized with outliner, in a secondary window.