In Super Mario Maker 2 you can change your character when creating courses. You can change between four different characters in Course Maker Mode, but the option isn’t actually in the Course Maker screen, you have to look elsewhere if you want to change your character.
Open the menu with + and then select the wrench option
The character change screen for Course Maker is actually located in the settings screen for Course Maker. You can access this by clicking on the wrench icon after you’ve open up the menu with the + button. The yellow icon on the right hand side of the screen can instantly be accessed with the + Button or you can hover over it and select it with the A Button.
Once you’ve opened this menu go to the bottom and select the wrench icon, which will open a new window that gives you some new options, such as selecting a different character. In the top right of this menu you will see an option for “Character” and you can choose between Mario, Luigi, Toad, and Toadette.
Hover over the character that you want and then press the A Button to confirm your choice. You will hear a audio notification that signals the character has been changed. Whichever character you select will instantly be switched to in the Course Maker screen