Press E to open Widget, Press again to close

First off, i dont have access to my pc so sorry, but first attach the end overlap to the close gate (gotta love being a smartass) but the way i do it is create the widget with beginplay and set it’s visibilty to hidden. And from the gate exit do a flip flop with A setting the widget to visible and B setting it to invisible (cant remember the exact node but i think its set visibility)
Hope this helps.

When overlap the box I can press E to see a widget. But how to remove the widget by pressing E again?

at the most basic all you need is a flipflop and a remove from parent node. as shown in the example below, with a flipflop the first time you press the input key it uses the A pin and the second time the input is presses the B pin is used.

its pretty simple though there are a few things to note, first you probably want to promote the widget reference to a variable, once thats done you may want to switch from a flip flop to a isvalid? type setup for more advanced implementations.

What about trigger box? How can make button available only insade the box ?

you could just add in a gate like your were doing, begin overlap open, end overlap close. or you could enable and disable input on overlap. heck you could even create and destroy the widget on overlap. its simple basic stuff.