There is no MATLAB function that would provide you the location of these tunable parameter within the generalized matrix. However, if the goal is to interact and change the value of these paramters, you can use the Blocks propoerties of the matrix. Refer to the following documentation link to read about the property:
If you need the location of the parameters, a hackish workaround is to use the usubs function to substitute the tunable parameters with unique identifiers and then identify their locations as shown below:
p = realp('p', 0);
A = genmat(zeros(5));
A(2,4) = p;
% Substitute the tunable parameter with a unique value
% This helps in identifying the location of the parameter
uniqueValue = 1; % Use a unique non-zero value
A_sub = usubs(A, 'p', uniqueValue);
% Find the location of the unique value
[row, col] = find(A_sub == uniqueValue);
