Hm, I've never heard it being used this way. If it IS frequently used, it should be added. However, if it's regional and not very common, the general idea here is not to add it.
I don't really understand why, since it's just an option for what the English speaker can input when translating, it will not be shown when translating English to Ukrainian. I would add even regional words. If someone says "case" for "suitcase", and he/she understood correctly what "валіза" is, why not?..
No but I'd say in this case (hehe), if a learner sees валіза and inputs "case" because he's more used calling that thing a case rather than a suitcase, it's fine. I see it as him understanding what валіза is, it's very unlikely he confused it with some other meaning of "case" :D