How to create a button that can be clicked and lead to the execution of a postfunction?

I would like lto create a menu item that can lead to a postfunction being executed once I click on it. I would like the menu item to look like the one shown below: 

I feel like the only way to have a menu item is to have a fragment but I do not need a REST API that goes with it, I just need a series of actions to be executed once I click on the button. I do not need a new page to be shown once I click on the button and I feel like the REST API is doing this. I feel like the REST API always goes with the fragment. Which one of the following options in scriptrunner would allow me to do this? 

One approach is to use a self transition in the workflow. That is, a transition that goes from the current status back to the same status. And then add the post function to that self transition.