What fun! I dug through my 20s cookbooks and can add these to the list
Waldorf salad
Banana and nut salad
Brown bread sandwiches (that is steamed brown bread- made in cans with a nice cream cheese filling)
Creamed salmon on toast
Rice croquettes with cheese sauce
Salmon croquettes
Ham croquettes
Cheese, pickle and pea salad
Riced potatoes
Scalloped tomatoes
Swiss Steak
Baked Hamburg Steak (this is hard boiled eggs baked inside a "roll" of burger with a tomato-based sauce over it)
Scalloped everything
Chicken Fricassee
Chicken A La King (on toast points or puff pastry)
Broiled kidneys
Baked eggs in tomato sauce
Welsh Rabbit
Frozen fruit salad
Puddings of all kinds
Fritters of all kinds
Rice Fan Tan (kind of like a firm rice pudding with candied fruits, cut in strips, dipped in egg then bread crumbs and fried in butter then sprinkled with powdered sugar!)
Tapioca cream
Floating Island
I find the gelatin salad craze didn't really hit until the 30s- in the 20s boiled dressings were the rage- also fresh fruits were becoming a little easier for Mrs. Housewife (!) to find so bananas, pineapple, grapes, grapefruit, oranges were very "hot".
If you need actual recipes, let me know.