Having trobule with casting to widget


I’m quite new to blueprints, so keep in mind that I’m not well experienced yet.
So let’s get straight to the points, I’m having problem with casting. Mainly with casting to widgets as title says. Right now I’m making inventory system, I have quite a lot of widgets and I need to communicate between them. Most of the widgets are childs of MainWidget. Well I dunno if I should call it childs, they are placed in MainWidget designer, so basically they are variables.
So basically if I’m not mistaken I only need to cast to MainWidget. I read that for the “object” input in Cast node is return value from Create Widget, so that’s what I did. But now it says 'MainWidget is already a ‘Main Widget’, you don’t need to Cast To Main Widget.

Creating widget:

Casting to widget: