This study highlights the effect of BaZrO$_3$ doping on (Na$_{0.52}$K$_{0.48}$)(Nb$_{0.95}$Ta$_{0.05}$)O$_3$ lead-free composition. The doping, interestingly, reveals the formation of a new polymorphic phase boundary between rhombohedral and tetragonalphases, while eliminating the orthorhombic phase. Rietveld refinement of temperature dependent X-ray diffraction data, in conjunction with dielectric studies, was utilized to corroborate the findings. The study also addresses in detail the process optimization methodology, involving calcination, sintering and poling process, which is highly relevant to the research community. Two mol% BaZrO$_3$-doped samples exhibited better piezoelectric, ferroelectric and dielectric properties. The doping also substantially improved the stability of properties during ageing, under thermal and cyclic electrical loadings.