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/

Nice research Odo! Of those, I know positively that all 5 nominees in Bonnie & Clyde were in a scene together, I think several scenes actually.

I would have to discount "The Godfather Part II", Robert De Niro and Al Pacino are never in the same scene.

Trivia from the 1995 movie "Heat"
"The first film to feature Robert De Niro and Al Pacino acting together, which created much hype prior to release. They both starred in The Godfather Part II (1974), but never shared the screen together as the split chronology prevented this. When this movie was finally released, even its advertising material promoted the film as a De Niro and Pacino "showdown"."

https://www.imdb.com/title/tt0113277/trivia/?item=tr0613300&ref_=ext_shr_lnk