Unfortunately, there is not a Default/Non-Default loading option as there was in EDEE. This is by design as it confused more people than it helped. The tree view is a simpler method which people understand when they want to do special loading situations.
The tree view itself is set up for swapping and loading/unloading, not for ordering. So if you desire to order a list of 50 units in a particular way, you will have more work to do. The tree view can be impacted by a machine that has difficulty rendering the scene.
Regarding various comments involving the mouse and the interface, first, all command and info buttons can be mapped to a key. The map itself can also be scrolled via keys. All of those commands and a few more can be set through key binding.
The dialogs and interface controls do have only rudimentary key controls, and they are not fully compliant with standard windows controls. Unity only provides very basic controls, which must be built upon. This involves a great deal of time, which is a short commodity for this project. So some of the basics are in it for now. Time will tell if more can be added.
EDEE, being a Windows OS dedicated program, was able to take advantage of the built in Windows API. Unfortunately, Unity does not do this, it has a homegrown kit which is very basic. This is one of the few disadvantages of using Unity. So a lot of the expectations of windows standards compliance are not going to be there, at least for now. Do not construe this as a defense for the things you don't like, it is just the reality.