@User: I had to look this up, as I had previously only implemented

sky130_fd_pr__nfet_05v0_nvt

in magic. The only layout difference between the two is an ID layer called LVID (GDS 81:60). I can implement this in magic and the sky130A.tech file and sky130A.tcl device generator. There should be two device types "mvnnfet" and "nnfet" corresponding to the 5V and 3.3V devices, respectively. Currently only "mvnnfet" has an extraction definition, but it is straightforward to add the 3.3V device.