I’m not sure about putting a checkbox before the number, but you can somewhat add it after the paragraph number using a wingdings font letter q, r, o, or p. Create a new character style with wingdings set as the font family. in the numbered list paragraph style set a nested style of your wingdings character style through 1 letter. Each time you have a new paragraph you will need to start it with one of those characters.
There may be a better and easier way to do this, but I don’t know it. Maybe someone could use this as a base to better achieve the result you want.