After I copied the original button (as an inherited FormField – CustomButton), the piecewise check that my _render() executes was passed.

After I saw a different design than the original button on the copied button, I looked for the reason for this.

The reason my CustomButton is not working as expected is the button for the setting process. If the “process button” property is set to “true”, it will not work. After I set it to “false”, my _render executed.

Thanks for your comments, this allowed me to exclude or check a few things, even though I came up with the solution in a different way.