Sure! I don't use JOSM a lot, so this might not be the quickest way to do it, but you can open up the Relations panel, then select all the disc_golf=hole ways and create a new relation with them, adding type=disc_golf_course as a relation tag. Then you can delete the type tag from the ways

Also, tees and baskets shouldn't have names, the hole number should go in the ref tag of the disc_golf=hole way. There's a well-mapped course here to look at as an example: https://www.openstreetmap.org/relation/14081231

Finally, make sure you add a node like they did here https://www.openstreetmap.org/node/2293235686 tagged as leisure=disc_golf_course to add the name, address, access, fee, etc. 

Hope this helps, let me know if you have any more questions!