  We aim to directly trace the vertical location of the emitting surface of
multiple molecular tracers in protoplanetary disks. Our sample of disks
includes Elias 2-27, WaOph 6 and the sources targeted by the MAPS ALMA Large
Program. The set of molecules studied include CO isotopologues in various
transitions, HCN, CN, H2CO, HCO+, C2H and c-C3H2. The vertical emitting region
is determined directly from the channel maps, implementing accurate masking of
the channel emission to recover the vertical location of the emission surface
even at large radial distances from the star and for low-SNR lines. The
vertical location of the emitting layer is obtained for 4-10 lines in each
disk. IM Lup, HD163296 and MWC 480 12CO and 13CO show vertical modulations,
which are coincident with dust gaps and kinematical perturbations. We also
present estimates of the gas pressure scale height in the disks from the MAPS
sample. Compared to physical-chemical models we find good agreement with the
vertical location of CO isotopologues. In HD 163296 CN and HCN trace a similar
intermediate layer, for the other disks, the UV flux tracers and the vertical
profiles of HCN and C2H are lower than predicted in theoretical models. HCN and
H2CO show a highly structured vertical profile, possibly indicative of
different formation pathways. It is possible to trace the vertical locations of
multiple molecular species that trace a wide variety of physical and chemical
disk properties. The distribution of CO isotopologues are found at a wide range
of vertical heights $z/r = $ 0.5-0.05. Other molecular lines are mostly found
at $z/r \leq $0.15. The vertical layering of molecules is in agreement with
theory in some systems, but not in all, therefore dedicated chemical-physical
models are needed to further study and understand the emission surfaces.
