IM-UFF: Extending the universal force field for interactive molecular modeling.

•An extension of UFF which allows to modify molecular system structures is proposed.•It uses weighted bonds and atom types to update topologies and parameterizations.•It helps to build and edit systems while being guided by physically-based forces.•The method has been evaluated on a large set of benchmarks.•It is proposed as a self-contained module for the SAMSON software platform.