We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.
You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
Go to your Steam Library and right-click Imperator and select "Properties", there in the "General" tab you'll see a "Set Launch Options". Click that and add without quotes "-debug_mode"
You can do what you did with the .exe too, so it'd be like "path_to_imperator/binaries/imperator.exe -debug_mode"