[2020] How do I increase the ammount of players connecting to my private world?

Hi everyone o/

Recently I stared playing another round of eco and started a new world on low collaboration (1-3 players) - now my friends wanted to join in but only two of them can join at the time and I can not get the 4th player in. I asume this is because of the collaberation setting since the 4th person can join if someone else disconnects..

Now the question is how to increase it to more players? I did some digging arround in the files but no coding programm I have installed is able to work with eco safefiles? Can I adjust the server settings somewhere or is there a programm I can manipulate the .eco file with?

Thank you in advance!