mass property
Mass of the node. By default, each node has mass equal to it's marker radius . Mass is used to determine how two connected nodes should affect each other:
Attractive force is multiplied by the ratio of two connected nodes; if a big node has weights twice as the small one, then the small one will move towards the big one twice faster than the big one to the small one .
API Docs: https://api.highcharts.com/highcharts/series.networkgraph.nodes.mass
Implementation
double? mass;