Fuel tank jettison is problomatic now. Using Jettison tanks all 3 go, pressing jettison stores has the same effect. In earlier versions FC1.3 Jettison of external tanks was different though not fully correct. In FC1.3 the first press of the stores jettison switch dropped the 2 wing tanks, a second press resulted in the cl tank going ... not correct but at least selective.
A way to implement this to at least be able to replicate an appropriate sequence would be:
Press Jettison tanks .... only the cl tank goes (as IRL)
Press External stores button .... Wing tanks go
Then for each successive press of the stores jettison button each weapon is jettisoned symmetrically inboard to outboard.
The most accurate solution would be for specific Keybindings for Cl tank jettison and Wing tank jettison.