As the title says I want to know how to add a custom operation in the drupal 8 book admin edit form's operations. I need this for my module in which I want to provide Add Sub Page operation for the user.
Upon clicking on the operation, I want to execute a function to add a new page to the parent page. I know how to add pages programmatically (Thanks to Lisa regarding help for adding pages in the book) , the only thing that I need is this operation entry in the drop down list.
Can somebody please help?