I have changed mouse controls a bit.

Left drag - rotate the camera (look around)
Right drag - rotate around the current object (orbit)
Middle drag - change the FOV
Left + Right drag - change the distance to the current object (zoom; works in the Map mode)

Left click - select an object
Right click - select an object and call context menu
Middle click - return previous/default FOV

Mouse wheel - change movement velocity

The context menu is slightly changes across different types of objects. If you select the "Moons" or "Planets" it opens the Solar system browser at the selected object's level (i.e. right click on the planet -> click "Moons" -> a browser with moons of this planet will be opened).

Also I have replaced an ugly purple loading progress bar with annoying messages with a small rotating icon near the FPS counter:

These loading messages are still shown in the Debug mode. This info was really needed only for debug purposes, there are many videos on youtube where people forgot to disable the HUD or change it to minimal mode with Ctrl-~. I think that this rotating icon looks much better and not so annoying.