Installation

If RimGui is not installed, please refer to this for installation.

Open the Package Manager from Window → Package Manager.

Select My Assets.
The image below shows Unity 2022.3.
The UI may vary depending on your Unity version.
my-assets

Select the RimGui Extensions package and click Install.

References are generally not lost, but if the reference to ManualSO in the ManualEntry object within the Scenes/Extensions Manual.unity scene is missing, please assign the ManualSO asset from RimGui.
manual-entry