Trouble using constant node with materials

I am trying to use a constant node (1+left click) to subtract the metallic sheen from a grass/sand material for a project. However, it does not let me input the value. The only way I can use a constant node and input a value is to right-click and select “convert to parameter”, which is not really what I want to do.

Any tips or tricks that might help? (I can post screenshots, but it is all just as you would expect it to be. I’ve watched several material-building videos on YouTube and I follow along exactly, but in the end it still will not let me input the value as they have it. Should not be any surprises with how I have created and connected the node.) Thanks!