An enhanced closed-form multilayer in-plane frame element is formulated, in which the inelastic axial-flexure-shear interaction is modelled with multiple embedded axial, rotation, and transverse coupled discontinuities at arbitrary positions along the element length. This multilayer element is an extension of the closed-form frame elements with multiple embedded discontinuities for thin and thick beam theories developed by [1,2], respectively. For deeper understanding and for the sake of simplicity, small strains, uniform external loads and quasi-static problems are considered. The variational model is solved by pure mathematics, which naturally leads to an original boundary value problem. Consequently, flexibility and stiffness matrices are derived in closed-form, which are symmetric, naturally condensed, positive definite in most cases and all their entries are non-zero values considering inelastic coupling using an innovative and simplified multilayer integration method for arbitrary cross-sections. This novel element drastically reduces drawbacks associated with traditional numerical simulations, thereby reducing computational cost and, when sufficient embedded discontinuities and layers are considered, providing high accuracy results with a single element. In addition, the developed element is free from shear-locking, tension shift effects are naturally included, and no mathematical algorithms are necessary to guarantee internal equilibrium. Application examples are presented to validate the accuracy and numerical robustness of the formulated element.