@itai What’s being discussed here is an actual patch for Blender, which brings a feature to Blender’s code. As such, it cannot be an addon. However, the functionality is being developed further here: X-Ray selection experiments build
You can download the Blender build and extract its contents to the folder where you (want to) install your software. Also, feel free to head over to that topic and post any feedback/ ideas related to the buid there.
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