https://bugs.winehq.org/show_bug.cgi?id=44826
--- Comment #23 from Nikolay Sivov bunglehead@gmail.com --- I'm planning on getting this in right after wine 6.0. So please test some more, for example one missing bit is diacritic marks reordering, that I think happens when you have more than one mark stacked, and order in which these are typed in should not affect visual order, or something along these lines. I realize it'd be easier to test if typing actually worked.
Regarding input handling, as I recall you had to install/enable language support for Arabic in Word explicitly, it has some UI with a list of languages it supports. After that Word detects input language using current keyboard layout, which for Wine means that switching layout while Word is running is not detected by the application. It should probably work if you switch to Arabic layout before running Word. I don't remember now how current locale affects this, it's been awhile since I tried.