How can I get components declared in C++ to show up in components tab in BP editor?

I just tried it, doesn’t work. Getting really frustrated with the engine. I did a test where I made a brand new blueprint, and with the new one, it DID work and I DO see my stuff showing up in the components list. But that’s not terribly useful…will I have to re-create my blueprint every single time I add a new variable to the C++ code? Why don’t the changes in the C++ code show up in the blueprint I already made that derives from that class? Why do I have to make a new one to see anything happen?