We reconsider the issue of search for a nonzero electric dipole form factor (EDM) ${d}_{\ensuremath{\tau}}(s)$ using optimal observables in ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ production by ${e}^{+}{e}^{\ensuremath{-}}$ collisions center-of-mass energy range from $\ensuremath{\tau}$-pair threshold to about $\sqrt{s}\ensuremath{\sim}15\text{ }\text{ }\mathrm{GeV}$. disc...