  This note is a complete library of symbolic parametrized expressions for both
real and complexified configuration spaces of a planar 4-bar linkage. Building
upon the previous work from Izmestiev, 2015, this library expands on the
expressions by incorporating all four rotational angles across all possible
linkage length choices, along with the polynomial relation between diagonals.
Furthermore, a complete MATLAB app script is included, enabling visualization
and parametrization. The derivations are presented in a detailed manner,
ensuring accessibility for researchers across diverse disciplines.
