Are you talking about the console command r.ScreenPercentage?
To achieve the effect on the left open the console with backtick/tilde.
` r.screenpercentage 25
Runtime DataTable : Import and export game data to and from CSV or Google Sheets while your game is running!
easyCSV : Read data from any CSV and put them in an easy-to-access string map!
iTween : Free, smooth, procedural object animation