In Data Objects Editor, I can use multibyte characters for "Label" of a field. The label is properly displayed in "Editor" tab. But in "Source" tab, the label is persisted as Unicode numbers. See UnicodeLabel01.png. After saving the Data Object and clone/pull via git, I can confirm that the source is the same (label as Unicode numbers). If I add another field, the previous label becomes proper multibyte characters. The newly added label is persisted as Unicode numbers. See UnicodeLabel02.png.

So the last added label is always left as Unicode numbers. If I use "Create and continue" in the New Field popup, multiple labels which are added at a time, are left as Unicode numbers.