There is an article on PTC https://www.ptc.com/en/support/article/CS211115
I've checked it on 11.2 - all works ok.
On 12.0 there is no problem with adding Custom WVS Scheduler Methods, but I have problem with part 'Publish Actions from Windchill Search result / Folder Contents table'.
Does any of you try to implement it on Windchill 12??