Sorry I haven't responded in all this time; I never come here, not since November or December, as no one ever posted here.
The head was originally going to say things, but this didn't make it to the final version.
To change the color of that map takes a lot of hard work, but to add trees, double click on the little tree icon in loathing (this is the scenery icon) and add a simple tree from the list. Then click on the other popup menu which allows you to select that tree, and then click on the map. Then you'll have as many trees as you desire.
When you add a new unit (same as with scenery), you get to type in a number for the team. In solos, the Light is labeled "0" and the Dark "1". Label your units accordingly for which side they'll be on. Btw, most of this stuff can be learned by just seeing how Bungie did it.
Don't even try to move units between games. It's so far beyond all but the most dedicated of Mythers, which is about a dozen people. Ask at MythVillage or perhaps somewhere else; mb one of them will decide to tell you.
The other two are not known. You should go to the Asylum at myth.bungie.org for virtually all of these questions, especially this one. GURPS Myth (an RPG book based off Myth) cited two other Fallen Lords, but the author pretty much invented them based on the pre-release info, so those names are not cannon. Basically, there are only four known.
Again, don't bother with trying to make your own units or maps, unless you really want to. Myth is virtually deserted in a lot of ways; by the time you develop the most meager of abilities, it may be completely dead .
Help lies in MythVillage, the Asylum, and The Mill, all of which are in the links of this old site. Gl, if you ever even read this.