I used the ArcGIS Pro SDK to create my Add-In project and to create the DockPane but the Esri Brushes don't show up as Dynamic Resources.
According to Esri (https://github.com/Esri/arcgis-pro-sdk/wiki/proguide-style-guide)
"ArcGIS Pro XAML styles should be used as DynamicResources while styling the UI elements in an add-in. Add this code snippet to your xaml so that these Dynamic resources will load in Design mode in Visual Studio."
<UserControl ... xmlns:extensions="clr-namespace:ArcGIS.Desktop.Extensions;assembly=ArcGIS.Desktop.Extensions" ...> <UserControl.Resources> <ResourceDictionary> <ResourceDictionary.MergedDictionaries> <extensions:DesignOnlyResourceDictionary Source="pack://application:,,,/ArcGIS.Desktop.Framework;component\Themes\Default.xaml"/> </ResourceDictionary.MergedDictionaries> </ResourceDictionary> </UserControl.Resources>
However, the SDK already puts this reference in the .xaml file but no dynamic resources show up in the Designer options. And manually typing in the Esri Brush name doesn't do anything.