Yes, widget blueprint is blueprint extended from UUserWidget class, here you have API refrence:
If you do that you need to add “Slate”, “SlateCore” module depnces in build script (*.Build.cs), if you never did that here tutorial:
Speaking of which, UMG is a UObject frontend of Slate which is UI framework design originally for editor, but you can use it in-game (You can see that via UMG). UMG only makes it accessable to blueprints, because Slate classes are outside of UObject envrament. Slate is a lot more usable in C++, the UI definitions looks a lot nicer and it easier to workwith, you will probably find more documentation and tutorials for Slate then UMG use in C++. Not to mention you will have 100% access to all Slate widgets (as long if they are not in some editor module, like graph editor), UMG only supports portion of it. So you might consider using it insted, here you have docs for Slate:
Here you got nice tutorial: