Decky HelixSR Manager has been released in version 1.0.0.
The Decky Loader plugin can be installed in Game Mode via Decky settings > Developer > Install Plugin from URL or from the zip file.
Decky Loader plugin. Install it in Game Mode: Decky settings > Developer > Install Plugin from URL, or from the zip.
See decky-plugin/README.md.

Source: GitHub