This command hides who holds casus belli on the contacts screen.
The Stellaris command contacts_summary is used to hide information about which entities or empires hold a "casus belli" against others on the contacts screen.
"Casus belli" is a term used in the game that denotes a reason or justification to declare war.
So basically, this command allows you to hide declarations of war in the contacts overview.
In Stellaris, cheats are executed from the command console, a text box that you type commands into.
To open the command console press the ~(tilde) key, which is typically located under ESC (escape).
If your keyboard does not have that key, or pressing ~ does not work, try the following keys:
Type your command into the console, and then press ENTER .