Its no possible in 1.10 to have two different Dialog+ Fields with the same value. This was possible in 1.9 versions though.
To reproduce create 2 custom dialog+ fields. For example use "SSH User Groups" und "SSH Server Groups".
In "Dialog-Admin" -> "Custom Dialog+" try to enter the same value (e.g. QA) into both. This results in the following error:
General error: Following values could not be saved because it would lead to duplicate entries: QA
Its possible to enter a numeric "0" into a dialog+ field via api but not via the administration ui.