bpmn-visualization already provides a CSS API but it requires the CSS styles are defined in the html page. Is this convenient for the R integration? the R package may not let R user to modify the underlying html page.

We may need bpmn-visualization to provide a new API that let style specific BPMN elements: process-analytics/bpmn-visualization-js#1030. This feature is available as of bpmn-visualization@0.33.0 which is bundled in bpmnVisualizationR 0.4.0.