warn when unsaved value remains in single line text input (list)

[lsteinmann]

in the editing modal, when one enters a new value into a "single line text input (list)" and does not click the plus button, the value will not be added to the list (which is expectable behaviour and should not change). however, it seems to happen quite often that people forget to click the plus button.

either the field needs to be redesigned to make it more obvious, or the modal should warn about not saving these changes when a value is present but not properly added (similar to the warning that appears when entering invalid values). same goes for all other input types that allow this (literature, dimension, ..?).