My assumption for it was that it would allow full movement on all sides. Because left/right need special attention too when using a grid list or similar.
Basically what @Everynone isn’t directly saying is that the default implementation of all widgets parts on their own as they are - flat out sucks.
This, however (for once), is by design.
By making the component as slender as possible you improve usability/programmability.
Whereas, always including every possible case scenario is bulky, unmanageable, and 90% if not 99.999% of the time isn’t needed.
Now to your issue at hand with the dotted stuff.
Step one is to disable auto focus stuff. Only way to truly remove the dotted line - if you search you’ll find specific answers.
Step 2, for an image hover, is to create a custom button that contains an Image, and assign an “hover” that gets swapped at runtime.
In my case, injust called this the wp_button (wp = widget part) and I use it as the “default”, because all of my UI buttons need some sort of a graphic.
In your case, or in someone else’s case, maybe the button really only needs text, and the default messy windows form look from the 90s is perfect for them. So they wouldn’t create a button with an image.
The process for handing custom input via BP is not an easy to implement thing. It’s not hard either, but you should probably set aside a week and only really try it after defining some standards / reading up on UI and UE4 best practices.
In the end, it’s really (like almost always, unless you are an engine developer, damnit!) “whatever works” if you are making just a one off… so trials and error does get you to accomplish the task (hence the arbitrary week time to figure it out).
[User OP had an unfortunate naming choice. Should probably ask the powers that be to change that tag to always refer to the post maker…]