The first expression is push(record.values.toppings ?? [], "chocolate chip")
and the second one push(record.values.toppings, "sugar", "sprinkles").
You can add multiple items to the array using the same push.
Note the first expression where I used record.values.toppings ?? []; this is needed as in my case the array could be non-existent in case I haven’t added anything to it.
If your field is required or you’re certain it will be populated you can omit the ?? [] bit, else keep it.
I tried your solution and it works for strings/number
however, it doesn’t work for the record selector !!
can you share an example for record selector type ?