Macroprocessing language loop through equations

Hello,

can I do something like this in mod file?
@#for eq_name in equation_list

@#for dummy_var in covid_varnames

equation[@eq_name] +@eq_name{RHS}_@{dummy_var} * @{dummy_var}

@#endfor

@#endfor

What exactly do you mean? What is that code supposed to do?

I have several equations and I would like to update them all by adding standardized set of dummies to each.

I want to loop through the equation tags, call for the associated equation, and concatenate dummies to it.

No, that is not feasible, because at the time of macro-processing, the equation tags and the associated equations are not yet known to Dynare.