No need any workflow.
Hope you already added AD in both vRA and vRO.
If so very simple to search AD user or AD user group in vRA form.
Created one input "appOwner" and type should be AD:User . And in vRo presentation tab add "select value as" and set "drop-down "
You can application owner name in vRo by appOwner.name
Why have you marked your previous answer as the correct one if you're still having failures?
You're failing because you have an input type of your action of type Array/AD:User but you're not supplying that anywhere so the output is null.
jeet11 You keep editing or bumping this post somehow and I'm not sure what you're wanting to do. Please explain what exactly you're trying to achieve and what your use case is here? Like most things in vRA, there are multiple ways to go about doing them. Generally speaking, it's not a good idea to let someone manually specify who the owner is of a deployment. This is why the support role exists with the "request on behalf of" function. Otherwise, the owner is set automatically at request time. Again, please explain completely and clearly what your goals are and why you want (or think you want) this functionality.