You can create EditorDescriptor which can set Order of the property. Here is how I change the EmailActor order:

[EditorDescriptorRegistration(TargetType = typeof(IEnumerable<EmailTemplateActorModel>), UIHint = ConstantsFormsUI.UIHint_EmailTemplateActorEditor, EditorDescriptorBehavior = EditorDescriptorBehavior.OverrideDefault)]
public class EmailTemplateActorCollectionEditorDescriptor : CollectionEditorDescriptor<EmailTemplateActorModel>
{
    public EmailTemplateActorCollectionEditorDescriptor()
    {
        ClientEditingClass = "epi-forms/contentediting/editors/EmailTemplateActorEditor";
    }

    public override void ModifyMetadata(ExtendedMetadata metadata, IEnumerable<Attribute> attributes)
    {
        GridDefinition.GridSettings["richTextColumns"] = new[] { "body" };

        base.ModifyMetadata(metadata, attributes);
        metadata.Order = 100;
    }
}

I tried to create an EditorDescriptor like yours but nothing happens. The sort index is still -5300 for my actor.

Can't figure out what I'm missing...

/Kristian

Could you post your code of the descriptor here? Could you set a break point and debug if it is running into your code?

I used your code and now it works. I finally got my actor where I wanted. I had to set sort order for the WebhookActor also. I think the sort order is acting kind of strange. The properties on the settings tab for the form is ordered very differently depending on what sortorder i give the emailActorModel. Sometimes the published, created and modified fields are on top of the page and sometimes in the bottom. In the database the sortorder still is -5300.

Maybe I'm looking at the wrong place.