We do not appear to be able to change the startup parameters for a new SQL Server instance, using SQL Server Configuration Manager (see screenshot below).
We are members of the sysadmin fixed server role, and are running SSCM version 2015.0130.16111.04 for Microsoft SQL Server 2016 (SP2-CU6) (KB4488536) – 13.0.5292.0 (X64) Enterprise Edition.
Best Answer
As stated in the comment, please check your privilege. This change you are trying to make will write startup parameters to the registry and need privilege beyond member of sysadmin role in SQL Server.
Ref: SCM Services - Configure Server Startup Options
Limitations and Restrictions
Security
Permissions
Configuring server startup options is restricted to users who can change the related entries in the registry. This includes the following users.