File extension $ has already been assigned the parameter $

What causes this issue?

You have entered a parameter name for a file extension for which there
is already a parameter.
The parameters of type 'PC' have the following function: At runtime
they have the information about which command needs to be carried out
on the PC to start the application belonging to the file extension. It
does not make sense to have several parameters for the same
application.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Remove the new parameter, since there is already one available which
carries out the required function.

Error message extract from SAP system. Copyright SAP SE.