Instead of only showing a button to switch to the texture properties - which don't actually allow creating a texture for linestyle - add a data-block selector that allows creating a texture for linestyle. It will also show a button to switch to the texture properties, if available. It seems like the previous UI didn't have any good way of assigning a texture for linestyle, without going into the texture node editor. Pull Request: https://projects.blender.org/blender/blender/pulls/141408