Some plot functions (e.g. rankingHeatmap) return a list of ggplot objects for each task, other plot functions (e.g. methodsplot (line plot across ranking methods)) only return a single ggplot object that contains all plots (multi-panel plot). It should be discussed whether this should be done in a consistent way to not confuse the end user. Would it be enough to document the return value properly? Does the user have enough freedom to customize a multi-panel plot?

The podium plot does not return any ggplot object. It uses the built-in plot function. How can this plot be customized afterwards?