[Q] one pair --- two bonds

Is there any way to connect one pair of atoms with two different bond styles
(for example FENE and harmonic). Sort of "pair_style hybrid/overlay" for bonds?

You might be able to list the same bond twice in
the data file and give it different types. The bond_style
hybrid command can assign different styles (FENE, harmonic)
to different types. I've never tried that; seems like kind
of a wacky thing to do.

Or you can use bond_style table to specify a single bond
which you tabulate in a file to be whatever you like, e.g.
a sum of FENE + harmonic.