Visual indicator for unique fields

[Augigauki]

I think it would lead to a slightly better editing experience if the end users were able to see that a field requires a unique value/input while they are editing, instead of only being notified after trying to save their document.

Could be displayed in a similar manner to the red asterisk indicating that a field is required, but maybe displayed as a yellow warning triangle or something similar could work.

I'm not a UX-designer, but in my mind this would lead to a more clearer and transparent editing experience less prone to errors for end users.