Trial and error, my friend. Trial and error. Even in being a noob modder (this is the first mod I have ever created, or even cared to create) I did not really ask how to do any modding within the program, but instead just went into the files and began changing things. Then I would go into the game and see what I changed. Always keep a second copy of the files you are changing in a different folder as countless times I have had to use them to undo things I changed. By doing it this way I have learned the limits of the program and pretty much what it will or won't allow me to do.
As for adding Research here is a brief walkthrough on how to include it into the game. It does not include everything, as writing such would be far too much to put here Instead, it is just enough to get whistle wet. I have used the research of my Urban Planet ability for the demostaration.
First make sure that the place you plan to put the new research is free of another. In the example below the block determines which block in the tree the new Research will go, with 0 always the first one. The first nummber in the pos moves the tech left to right and the second number moves it down, with 0 again being the first. The Research Field will allow you to put it into the noncombat, combat, or fleet trees. Also there is a line with a tier number in it. Just make sure this number is the same as the first pos number to assign the appropate Tier to the Research
pos [ 2 , 1 ]
After you have created the Research you must assign which race will research it, and there for you must edit the player file, as in the example below I show you a part of the PlayerTech.entity file. Add one to the count for each research you enter and put and additional entityDefname line in there including the file of your research. Below you can see PLANETCITY file that I created.
And SHAZAM!! You have a new research. Take note that you still need to assign what the Research does, as it would do nothing at this point, as well as change the hud icon, edit the english file in the string folder, designate what ability is unlocked by research and build that file if needed, edit the float modifyers and bool modifyers, etc, etc. There is alot more work to be done, but the game at this point should reconize your new research.
Hope that answered your question on how to add new techs.