Custom refiner based on list

Question

The scenario (2016 on prem): I have a set of lists which all contains some items. I have set up a search query which limits results to items from selected lists within the same site.

I would like to present some refiners for the user to easily filter the search results. For instance I have a list called companies and another called plants. Can anyone please explain (farily detailed) how I would set up custom refiners in order for the user to be able to click "companies" and only see results from the company list?

Answer 1

I ended up creating a site column with the list names in and adding it (hidden) to each list with a default option matching the list name. Then mapped it to a RefinableString and after a full crawl it shows up nicely.