This tool allows to add/remove/intersecs in some specific ways an atom selection to the current Selection.
It
is possible to select atoms on the basis of several criteria (atomic
specy, B factor, occupancy, distance from an atom ....), and to add,
exclude or intersects the corresponding hits from the current
selection. This way almost any specific or complex combination of atoms
can be achieved. Furthermore, checking the "Activate selection using
the tree" allows to add supplementary atoms by selecting them from the
"Object tree" tool, or checking the "Activate manual selection" to add atoms on the basis of clicks on the molecule directly.