There is broken link in the documentation in two places of the User's Guide for CRW v2.4:
*1. User's Guide

• 4.1.2.3. Che-Theia plug-in capabilities*
  —
  See https://access.redhat.com/documentation/en-us/red_hat_codeready_workspaces/2.4/html/administration_guide//using-a-visual-studio-code-extension-in-codeready-workspaces_crw.
  —

*2. User's Guide

• 4.1.5.1. Embedded (or local) plug-ins*
  —
  To include a Che-Theia plug-in as embedded, define a URL to the plug-in binary file (the .theia archive) in the meta.yaml file. In the case of a VS Code extension, provide the extension ID from the Visual Studio Code marketplace (see https://access.redhat.com/documentation/en-us/red_hat_codeready_workspaces/2.4/html/administration_guide//using-a-visual-studio-code-extension-in-codeready-workspaces_crw).
  —

The correct link should be by my guess to:
https://access.redhat.com/documentation/en-us/red_hat_codeready_workspaces/2.4/html/administration_guide/customizing-the-devfile-and-plug-in-registries_crw#using-a-visual-studio-code-extension-in-codeready-workspaces_crw