There is no way to automatically separate a string from any fields into individual words. (Unless they always have the same number of characters every time, which is unlikely.)
There are a number of ways to approach doing this, usually by adding one more step. One way is just add the WordA WordC keywords in a second Metadata Template. OR a different approach is to add the {event} variable to the keywords, and make the additional step a "Find and Replace" (macOS: ⌘-Shift-f, Windows: Ctrl-Shift-f) on the Keyword field where you Find WordA WordB WordC WordD and Replace with WordA WordC. The settings to apply Find & Replace ONLY to the keywords field would look something like below (note the checkbox to search "metadata" and checking the box for "keywords" field:
Hope that helps.
-Mick
