Lovely Charts is a free web-based tool for creating flow charts, site maps, network diagrams, and other visualizations with a drag-and-drop interface and a look somewhat upscale from black-line ...

Creating flow charts is not always ... can highlight it by clicking on a diagram. Doing this should allow folks to make changes to the connector, text, among other things. In the Graph menu ...

Further, while process flow diagrams (PFDs) are well understood by that name, piping and instrument diagrams (P&IDs) may exist under various other names or variations, such as mechanical flow diagrams ...