You should be able to get the specific leeches from this script: [Userscript] WaniKani Open Framework Additional Filters (Recent Lessons, Leech Training, Related Items, and more)
It was built specifically to work with the Self Study Quiz script, but in theory it should work with other scripts as well. If Self Study Quiz doesn’t give you what you want, maybe someone has a script that just lists out the items indicated by filters like the leech filter.