What you refer to as *panel *is a list of function parameters. Do consider studying the link I posted and have a look at this one, too - it will answer a lot of your questions:
https://docs.unrealengine.com/en-US/…ons/index.html
For a tl;dr:
Select the nodes you want to have in a function, right click on any one of them an choose *Collapse to Function - *this will automagically create a function and incorporate the selected nodes. You will need to add the attributes to the panel. You can then plop that function anywhere in the graph and adjust the attributes as needed.
The ***Input and Output Parameters ***section in the above link explains it better than I ever could!