Very useful; but it has two problems:
1) privacy
2) like other similar tools (offline sw), it does not have a graphic element which represents... a sub-diagram (which should be opened on double-click) and a Treeview for the entire project (I watched it a few seconds, but I think this is so).
In addition, some of these tools are able to generate source code, for example ArgoUML, which will be able to generate B4J code... VERY SOON
View attachment 44569