I did follow what you are asking. I re-created the tables/formulas, and see what you mean. I found a hacky workaround, which I’ll put below, but others may have a better idea. Also, maybe the team at Coda wants this implemented in a more direct way.
I created an extended version of the Menu table:
In the Fix 1 Column, I had the following formula:
I repeated this formula in the Fix2 column, but replaced the 1 with a 2. This pattern could be repeated to account for the total number of Food Groups that may be possible. Effectively, this broke out all the groups in the Select Group column into individual parts by grabbing the first group, then the second group, etc.
I then changed the formula in Choose Item to this:
This formula looks at the two new columns, which led to this:
You can extend the OR expressions in the Choose Item formula as many times as needed if you have more columns.
You can then hide the “Fix” columns or create a view if you do not want them showing up.
Again, very hacky, but worked for me. Hope this helps.