I'm curious to know if you have solved this problem using the Javascript API.
I am trying to do a similar thing. I have a protractor test that runs the spell check in a TextArea field. I can select a misspelled word and bring up a context menu with a list of suggested spellings. The menu appears but I can not select any item in that list. My code looks like this:
actions.mouseMove(textArea).perform();
actions.click().perform();
actions.sendKeys(Key.chord(Key.SHIFT, Key.CONTROL, Key.ARROW_LEFT)).perform();
actions.click(protractor.Button.RIGHT).perform();
// select the first suggestion (should be misspelling)
actions.sendKeys(Key.ARROW_DOWN).sendKeys(Key.RETURN).perform(); // <-- THIS FAILS! CAN'T SELECT ANYTHING IN THE MENU
expect(textArea.getAttribute("value")).toContain(spelledNote);
And, by the way, the menu is not a custom DOM element menu. It is just the native context menu that comes up in Chrome (Electron actually)
Thanks,
Louis