Does anyone have a slick way to search the Gospels for all the incidents (eventually harmonized) when Jesus had a meal with others, especially with unbelievers?
When I approach these types of questions, I like to start with the general and work my way to the more specific.
The first step I took when approaching this was just to simply find verses that mention Jesus eating. See image below for this search.
One of the search hits is Matt 9:11. This is a great passage about Jesus sharing a meal with tax collectors and sinners. It also has an interesting phrase, "reclined at table" (ESV).
This spurred me on to right click in this phrase to see what data might lie behind it. This revealed a topical tag "eating a meal."
From here we can launch the Factbook on this topic. This Factbook page is amazingly rich with all kinds of data that I think will be helpful to you. One place in particular is the Sense section. Here you can find all the places where the sense for "eating a meal" or "reclining at table" are used in the Bible.
After looking at the results from the above study, I was also able to craft this little search that may be of use. See image below.
Hope this helps.