What: A screen, maybe tab on the empire screen (F1) or somewhere else, where you can track: 


Colonizable Planet Types.

Terraforming paths.

How many planets of each type you have colonized

How many of each planet type you have discovered

How many of each planet type that you have discovered that is still availabe for colonization (ie system not owned by another faction) 

maybe more...


Why: Because it is not always immediately obvious which planet types you are able colonize. Without carefully looking at what you have researched or looking through planets in systems.

In regards too showing the terraforming possibilities its just nice to have an overview of what terraforming paths are possible.


This could be achieved by having something like this http://guides.gamepressure.com/endless_space_2/gfx/word/523814400.jpg or something similar using round pictograms for each planet type like on the technologies in the research overview. 


You would have: 

Arrows depicting the possible terraforming paths between the planet types. 

Highlighted colored circles around the planet types or maybe checkmarks to show colonizable planet types.*

Numbers at each planet type that indicate colonized, discovered and available colonization targets of each planet type.


*Planet types you can colonize because of an ecologist goverment should be depicted in a distinct way such that you can see wich planet you can colonize with an without the forced ecologist law. 


The information could be dislayed in other ways than I described... The essential part is to give an quick overview over what planet types you are able to colonize and the terraforming paths. 

Feel free to give other suggestions for the layout or information that could be contained in such a screen.