Can someone please tell me how do we write in dynare if a symmetric equilibrium condition has first derivative in it?

for instance : the equation q = 1-s-s1*lambda(+1)

where s1 is the first derivative of s. Should I specify the first derivative as a variable or as a parameter?

Typically, there is another equation defining that derivative. Hence, it is a variable. For example, lambda typically is the derivative of the utility function with respect to consumption and we have a defining equation of the type:

Thanks! I got it now… I am now denoting both s and s1 as variables.