L subshell fluorescent X-rays in Dy, Ho, Er, Lu, Ta, W, Pt, Au, Hg, Pb and Bi have been measured using synchrotron with selective creation of electron vacancies in individual subshells. Coster--Kronig (CK) yields were derived from the measured intensities. Present measurements have been made at photon energies above the edges where differences between measured and theoretical attenuation coefficients are almost negligible. Parametric trends for the results with $Z$ were developed to cover all $Zs$ in the range of 66--83. The trends predict the switching-off of L1--L2, N1 transition at Z = 67. The extent of fall/rise of $f_Lij$ values corresponding to off/on of certain transitions is found inversely proportional to the difference in binding energies of two consecutive subshells involved in the transition. For $Zs$ above/below these rises/falls, $fL_13$ and $fL_12$ values are almost constants. $f_L23$ values involving no break at $Zs$ follow the general photoionization behaviour that ionization probability is highest at the edge energy and decreases with photon energy. Yield measurements with synchrotron radiation for Dy, Ho, Lu, Hg and Bi and experimental values for $f_L23$, $f_L12$ in Lu and for $f_L13$ in Ta are being quoted for the first time.