I already knew In Opus, the setting you want is Hide file extension in Filename column, on the Display tab of the Folder Options or Folder Format editor:
However, when renaming a file, the extension is automatically shown again.
Is there any setting in DO to hide the extension even when renaming?
In Details mode, it will keep the extension hidden (unless you do something like push Ctrl-E to select the extension part, which will reveal it).
Looks like you're using List mode from the screenshot, which doesn't do the same thing. I've made a note to check if that's intentional (maybe because there's no possibility for a Type of Extension column in List mode) or can be changed.
Thanks for your reply.
I found other mode except Details mode will makes extension keep showing when renaming.