The "pie.stack" value passed to the type argument of the trackViewer package lolliplot function allows to rendering variants annotated w.r.t. some stack.factor legend co-variates (e.g. patients' source).
As is, the lolliplot dots are plotted according to a vertical grid that is set by the stack.factor value. A vertical gap distance is rendered in the y-axis which accounts for the non-occurrence of the given variant per the stack.factor value.
Which arguments and/or which script of the trackViewer package would need to be edited in order for the dots to be lined up on top of each other rather than interspaced by the stack.factor value.