As mentioned in the Jira cloud Xray documentation, user should be able to edit the values in the parameters list

As mentioned in the Jira Cloud Xray documentation, users should be able to edit the values in the parameters list.

This inconsistency between the documentation and actual functionality affects the usability of the parameters list management at the project level

Project Settings: Parameter value lists - Xray Cloud Documentation - Xray

Steps to Reproduce: Navigate to the project > Apps >  Project settings > Parameter value lists > Edit the Parameter list > Try to edit the existing values (Unable to add). 
Please refer to the attached GIF