I don’t know why but I was doing a project, and maybe it was my mistake that I accidentally removed the brush option under appearances in the detail panel of image in widget blueprints. How can I bring it again?
You didn’t remove anything. In the first pic you attached, you’re looking at the details panel of the Image widget, in the second it’s a Button - their Details panels differ quite a lot.
If you’re ever looking for a specific option, you can always use the Search field at the top of the window - that will narrow it down.