How to enable “Manual” in sequential optimization?

I have SQX Ultimate 142. In Optimizer – Sequential optimization there are two options for Parameter settings: 1) Manual, 2) Automatic. In my screen, only the Automatic option is enabled. The “Manual” option is grayed out, meaning it’s not available. Please, I want to know how to make the option “Manual” enabled. Any help would be appreciated. I already tried options like: parameters as constants, parameters as variables, parameters as random numbers in a template. Thanks in advance.

The manual settings has been disabled intentionally. The automatic is sufficient for the analysis since you test range of value around the original parameter value that can be determined automatically