Stellaris planet_size command

This command changes the size of the selected planet, can go above regular sizes but above 78 will move the planet backwards.
Command syntax
planet_size <span class="parameter parameter-primary">Size</span>
planet_size 40
How to open the console in Stellaris
Press the ~ / ` key to open the command console. This key is located at the top left of the keyboard, usually under the F1 or ESC key. Type the command and press the Enter key.