Finding Quintuple Planetary Alignments with SkyField
This is not an answer.

I computed all major planet conjunctions in DE431 to answer How to calculate conjunctions of 2 planets and you might be able to port what I did (using CSPICE) to skyfield.

Several of the more interesting conjunctions I found are here:

http://search.astro.barrycarter.info/table.html

including 5 and 6 planet conjunctions:

http://search.astro.barrycarter.info/STELLARIUM/stellarium-191.ann.png
http://search.astro.barrycarter.info/STELLARIUM/stellarium-092.ann.png

I note that the 6 planet conjunction is unique in DE431, but I refer to the 5 planet conjunction as "rare", so it's likely there's at least one other one.

I'm too lazy to look through my own results, but this might give you a start.