If you are just trying to change/create a component using Blueprints, why you don’t create a Blueprint Actor Component? When you create a new blueprint, instead of choosing Actor, you choose Actor Component, as in the picture below:
As a result, you have created a component that you can attach to other actors and that you can customize/program it in Blueprints.
In fact, you can inherit from any class (and for this I suggest you to become familiar with the Unreal Gameplay framework here Gameplay Framework | Unreal Engine Documentation ). Moreover, you can also inherit from the blueprints you create (you can have a look in the content example here 2.5 - Child Blueprints | Unreal Engine Documentation ).
On the other hand, if your question is: “I already have a component written in c++, and I want to modify it. How can I do it?” I would say that you can still inherit from it, and try to override the functions you want to change. However, to have a fine control over it, you need to learn c++, since there is no way to convert a c++ class into a blueprint one.
Hope this answers to your question.