Decal Brush is only available in UE5.3 and newer as the required blueprint nodes are unavailble in earlier versions of Unreal Editor.
Upgrade your project to 5.3 or newer for Decal Brush and example levels shown below
Required Epic Plugins
You need to enable the following Editor plugins by Epic Inc. for Decal Brush to work:
Geometry Script
Scriptable Tools Editor Mode
Scriptable Tools Framework
Steps for enabling required plugins
To enable these plugins do the following:
Edit
Plugins
Search for
Scriptable Tools Editor Mode
Scriptable Tools Framework
Geometry Script
Enable these plugins and restart the Editor
Show Scriptable Tools
To view the scriptable tools bar and use Decal Brush do the following:
Show Scriptable Tools
Click on Selection Mode
Select Scriptable tools or press SHIFT+9
Click on the Decal Brush icon and you can start using it