Success!
Using @AmberV 's keystroke iteration (but adding a final down key press), I could write a script for AutoHotkey to automate the navigation. This is the first time I’ve tried AutoHotkey; I’ll probably use this approach as a workaround should I encounter any more accelerator key collisions in Scrivener until the developers sort this out.
With this solved, I added a button to Stream Deck to execute the AutoHotkey script with the push of a button. It goes alongside the button to turn straight quotes into curly quotes. They are enjoying each other’s company. 
In case it’s helpful, here is the script for AutoHotkey:
if WinExist("ahk_exe Scrivener.exe")
{
WinActivate ; Activate Scrivener
Sleep 100 ; Brief pause to ensure the window is active
Send "!e" ; Press Alt+E to open the Edit menu
Sleep 200 ; Allow time for the menu to open
Send "{Up}" ; Navigate up one item
Sleep 200
Send "{Up}" ; Navigate up another item
Sleep 200
Send "{Right}" ; Open the submenu
Sleep 200
Send "{Down}" ; Navigate down another item
Sleep 200
Send "{Enter}" ; Select the option in the submenu
}