BitCy.
Just to explain that what you want isn’t possible using Keynote’s own AppleScript implementation. The only hope is to use “GUI Scripting”, ie. faking the clicking of menu items and buttons in the application as it appears on screen. This is a bit of a hit-or-miss process as an application’s layout and text content can vary from version to version, system to system, and user preference to user preference.
Yvan’s script is simply a test to find out what’s in your menus when running in English. On my machine (running Keynote 9.2.1 in Mojave), it also opens the “Export Your Presentation” sheet with the “Movie” pane selected. If you run it with a Keynote document open and look in Script Editor’s “Replies” pane, you should see something like the following, which could help Yvan to develop a script for you:
tell application "Keynote"
localized string "1543.title" from table "MainMenu"
--> error number -1708
«event ascrgdut»
--> error number -1708
localized string "1543.title" from table "MainMenu"
--> "Export To"
end tell
tell application "System Events"
set frontmost of process "Keynote" to true
get name of every menu bar item of menu bar 1 of process "Keynote"
--> {"Apple", "Keynote", "File", "Edit", "Insert", "Slide", "Format", "Arrange", "View", "Play", "Share", "Window", "Help"}
get name of menu bar item 3 of menu bar 1 of process "Keynote"
--> "File"
get name of every menu item of menu 1 of menu bar item 3 of menu bar 1 of process "Keynote"
--> {"New…", "New…", "Open…", "Open Recent", missing value, "Close", "Close All", "Save…", "Save As…", "Duplicate", "Rename…", "Move To…", "Revert To", "Export To", missing value, "Reduce File Size…", "Advanced", missing value, "Set Password…", missing value, "Change Theme...", "Save Theme…", missing value, "Print…"}
get name of menu item 14 of menu 1 of menu bar item 3 of menu bar 1 of process "Keynote"
--> "Export To"
get name of every menu item of menu 1 of menu item 14 of menu 1 of menu bar item 3 of menu bar 1 of process "Keynote"
--> {"PDF…", "PowerPoint…", "Movie…", "Animated GIF…", "Images…", "HTML…", "Keynote ’09…"}
get name of menu item 3 of menu 1 of menu item 14 of menu 1 of menu bar item 3 of menu bar 1 of process "Keynote"
--> "Movie…"
click menu item 3 of menu 1 of menu item 14 of menu 1 of menu bar item 3 of menu bar 1 of process "Keynote"
--> menu item "Movie…" of menu "Export To" of menu item "Export To" of menu "File" of menu bar item "File" of menu bar 1 of application process "Keynote"
end tell
Result:
menu item "Movie…" of menu "Export To" of menu item "Export To" of menu "File" of menu bar item "File" of menu bar 1 of application process "Keynote" of application "System Events"