How to get KATE's Spell Checker to show all misspelled words?

I found several reports of this bug. Listing here, here and here.

However, there is a workaround. You need to disable Enable autodetection of language from Settings -> Configure Kate -> Editing -> Spellcheck tab.

Then it will detect the error if you go to Tools -> Spelling -> Spelling. But auto-detection doesn't work sometimes. You can make this menu a shortcut by using Settings -> Configure Shortcuts menu.