How to save custom node?

Hello,
I created a custom node by selecting a group of nodes and right click to create one.
I created a new category and it is seen now on the left add-on panel. But I need to save it outside, also to copy inside Refinery folder.
I couldn’t seethe stored .dyf file. How can I save it?

Thanks,

Edit: https://primer.dynamobim.org/en/10_Custom-Nodes/10-3_Library.html
found this and tried it but it gives the error as I Can’t publish it because it’s in a package.