RAR split volume
Hello all, my usual google-fu isn't working so here goes.

I'm curious as to whether there are additional steps to crack .rar files that have been split into multiple volumes.

I did a quick test of making an encrypted archive of a file and again by splitting it into two volumes. All three files when used with rar2john will produce three different results. Running hashcat on these will only get me the expected result from the archive file that is whole which leaves me wondering what to do with what I need to do with the archive that has been split up into multiple volumes.

My guess is this is merely a functionality that needs to be added to rar2john. After that I presume neither hashcat nor JtR need any change. You might want to open an issue at https://github.com/magnumripper/JohnTheRipper (enhancement request).
Ok, I shall open one up. I saw a recent change to 7z2hashcat a couple months ago which was a similar issue with dealing with split volumes so I don't think it would be too difficult hopefully