Is it possible to create custom dropdown field with dynamic data?

Yes, end users must sign in to help center. So that is the problem. I cant see any possibility to get user's email. Is there any way to do it?

Thank you, Tipene, i'll try to clarify what i want to implement.
There is a hosting where users can rent dedicated servers, bare metal servers etc (devices it the context of that hosting). I want let people to use help center to report about issues they meet using their devices. And i want that user can choose with which device he has problem so that agent could see this information in a ticket. 
So i want to pull a list of user's devices from hosting using api and put them in ticket form in help center. For that i need somehow take user's email and make a request to api endpoint and then put user's devices in dropdown list.

Thanks for the context, Phil Phil. There's certainly ways we could make this work by having additional calls to the Tickets API to create the parameters and add them to your custom form based on the users email address. That said, that approach would be quite convoluted. If you could share the specific use-case that you're working towards solving, there may be simpler way to approach this.

Tipene

Hi, Tipene.
I want to have custom form in my help center. In this form i need to have drop down list with custom parameters depending on user's email (I will use the email to make request to external API to get information for my dropdown). Is it possible to do in zendesk?

Hi Phil,

Thanks for reaching out!

Could you let me know in a bit more details what you're wanting to do? Is the dropdown going to be a custom ticket form, or something like a navigation element?

Thanks!

Tipene