Changes in new UI - docking windows and in context menu

[micheus]

1) I can't seem to (re-)dock windows anymore. I had some windows docked, but on closing and reopening them, they just float.

When you close a docked window the information about it (size, location,..) is no longer available. So, when you open the window again (via Windows menu) it will be floating - that is the correct behaviour.

And I can't seem to resize or move the main Geometry window at all.

The main Geometry will always be "docked" -it's "part" of the main Wings3d window - you will never move it. You can move (dock) the other windows around it and use the vertical our horizontal splitter to resize them.
The layout is proportional (% of main window), so adjust first the main window's size and then dock and arrange the docked windows. I recommend you do that from right to left and top to bottom. (thinking about rows and columns arrangement)

I did read about holding the shift key down, but it doesn't seem to do anything.

It does. When you just open a dockable window and you move it over the main window then it will automatically enter in "docking mode". To avoid that and keeping the window floating you must to keep the SHIFT key pressed while moving that window.

2) Is the "Select" context menu gone (maybe a few versions ago)? Or maybe moved? Or am I just failing to access it?

You are talking about that selection bar (with icons) in the top the context menu, right?!
Yeah, it's gone. The old UI was a custom one and that allowed us to have that kind of mixed menu - we drawn it. The new UI uses the OS resources and that kind of option isn't available. (The v1.5.4 was the last stable one to use the old UI).

If you want to see a summary about the additions and changes for each version take a look here.