What film had the most Oscar nominees appear on screen together at the same time? (Note: not people nominated at different times for different movies, but all nominees for the very same film, together in a single scene(s).)

There are nine films that have earned 5 acting performance Academy Awards. Whether all the nominated actors appeared on the screen at the same time is difficult to determine without close scrutiny of each film. The films are:

Mrs Miniver (1945) - Greer Garson (W=won), Teresa Wright (W), Walter Pidgeon, Henry Travers, May Whitty.
All About Eve (1950)- George Sanders (W), Anne Baxter, Bette Davis, Celeste Holm, Thelma Ritter.
From Here to Eternity (1953) - Frank Sinatra (W), Donna Reed (W), Montgomery Clift, Deborah Kerr, Burt Lancaster.
On the Waterfront (1954) - Marlon Brando (W), Eve Marie Saint (W), Lee J. Cobb, Karl Malden, Rod Steiger.
Peyton Place (1957) - Arthur Kennedy, Hope Lange, Russ Tamblyn, Lana Turner, Diane Varsi.
Tom Jones (1963) - Diane Cilento, Edith Evans, Albert Finney, High Griffith, Joyce Redman.
Bonnie and Clyde (1967) - Estelle Parsons (W), Warren Baetty, Faye Dunaway, Gene Hackman, Michael J. Pollard.
The Godfather: Part II (1974) - Robert De Niro (W), Michael V. Gazzo, Al Pacino, Talia Shire, Lee Strasburg.
Network (1976) - Beatrice Straight (W), Peter Finch (W), Faye Dunaway (W), Ned Beatty, William Holden.

According to the quoted source, no film has received 6 Oscar acting nominations.
https://collider.com/movies-received-five-acting-nominations-oscars/