QuiltiX is a node-based MaterialX editor.
Have a look at QuiltiX – an open-source node-based MaterialX editor presented by Richard Frangenberg, the Prism Pipeline founder and TD, and Manuel Köster, Senior Technical Artist at Remedy Entertainment and Prism's Pipeline Developer. It is "designed with artists in mind" and has a customizable interface.
The tool will help you create and edit materials, preview them in the real-time viewport based on OpenUSD's Hydra, and then export them for use in compatible renderers.
As the creators note, QuiltiX can be integrated into existing studio pipelines to add additional features like library panels or publish processes.
If you aren't familiar with MaterialX, it is "an open standard for representing rich material and look-development content in computer graphics, enabling its platform-independent description and exchange across applications and renderers."
Recently, Academy Software Foundation (ASWF) announced OpenPBR, a shading model based on MaterialX that will be the successor to Autodesk Standard Surface and Adobe Standard Material, so you might want to check it out as well.
ASWF wants to advance open-source software development across image creation, visual effects, animation, and sound technologies. It adopted OpenImageIO as its hosted project and is working on its Open Review Initiative, which aims to build "a unified open source toolset for playback, review and approval of motion picture and related professional media."
If you'd like to try QuiltiX out, you need Python 3.9+ and compiled versions of USD and MaterialX. The tool is free, and you can find more about it here.