When creating parameters using formulas, the number of characters of the expression is limited to 80 characters. If you encounter this limitation, what you can do is to create additional parameters for each term of the expression and then put them together.
Ex: Instead to create P= a²+ab+b²+ cy+d+ ez+g, you can create 4 parameters as follows:
P1=a²+ab+b²
P2=cy+d
P3=ez+g
P4=P1+P2+P3
