I had to modify some of my stuff temporarily, so ignore the excess stuff in the images, but try this:
Overview: You have a variable that exists and can be changed in a character bp, a widget bp casts to the character bp to access that variable, and based on that variable the widget will change the visibility of its component(s).
1.) Create a button in a widget blueprint
2.) Click the binding drop-down next to the visibility option in the designer tab (not event tab)
3.) In the drop-down bar, click create new binding and name it something that has to do with visibility. This is a function, and you can also use this for other elements in the widget too if you want. (In my picture, I use “stage 1 visibility” as the same binding for multiple buttons/borders/fill-bars/etc.)
4.) Stop doing stuff in the Widget bp, and open up your character bp and make some boolean variable.
5.) On “Q” or whatever, make the boolean true when pressed, and off when not pressed. This will make the button appear when you press and hold Q.
6.) “Create Widget” and “Attach to Viewport” in the character bp for the widget you’re using.
7.) Return to the widget and cast to the character bp to access the boolean value you made. (This can either be done in the function, or at construct like in my pictures and you simply save the character reference. Both work.)
8.) Drag from the input pin of the function return node to create a “visibility” variable, and use the boolean from the character blueprint to change the visibility variable’s value.
9.) Make sure the button in the designer tab has the binding set to your function…
Widget Event Blueprint (above)
Widget Function Binding
Character Blueprint
Widget Blueprint (Designer tab)