UI Toolkit - Render Texture on Panel Settings makes it impossible to reuse

For outputting to a render texture, having the target texture on PanelSettings makes reusing the panel settings impossible. Would it not make more sense that the target texture is set on the MonoBehaviour UIDocument?

The PanelSettings assets makes it possible to reuse the same panel resources with multiple UIDocuments and render them at the same time. That allows UITK to batch multiple documents together, share the same Texture Atlases, without imposing restrictions on the scene hierarchy.

That unfortunately means that they need to be rendered into the same render target as well, so you need to create a copy of it, and all its other parameters in order to use another render target.

You can have a look at Presets to help managing default values that can be shared between different assets in your project: