Adding Vertical Text is not a way to make some "workarounds" easy (e.g. Pressing "Enter" after each character).
For sake of non-CJK users, "Pressing "Enter" after each character" DOES NOT create same output as vertical textbox does, since:
Letters will not be properly center-aligned
Some letters' (like periods "。" and commas "、") positions differs in vertical/horizontal text
kerning, or spacing between certain letters doesn't work
how should we write multi-line texts?
So "Pressing "Enter" after each character" is not even a workaround. I am afraid Affinity members are not looking into this functionality lack since they think there are known workarounds.
As rayRyo pointed out, vertical text is critical for Designer and Publisher usage.
For me, I would like to use vertical text for posters and video thumbnails, but Affinity products are not for them currently.
This is very sad.