Correct, please keep in mind that there really isn’t “one good way” to use all this. Visual Paradigm is an extremely extensive tool, I’ve been using it for years and I still learn new things about it from time to time (like with that post from Antony which I still think is really intriguing).
Also noteworthy is that Visual Paradigm provides several tools throughout all diagrams which you can use to enhance your work. Sometimes those have nothing to do with the diagram at all but more so with what VP has to offer (think about the freehand section in the palette).
It used to be the place where you’d specify the name of the current diagram, but to my knowledge this option isn’t being used anymore, it only seems to reference the so called root frame of a diagram.
I sometimes see it pop up when I’m working with VP within NetBeans where VP uses the previous GUI layout. and within BPMN but I can’t find a direct connection between that and the active diagram. On my end it always says “Unspecified”.
Can’t really answer this because I’ve never seen this happening myself before. Worst case scenario I can think off would be to create a new diagram and then using copy/past to move the current elements over.
The ‘a’ and ‘M’ indicators mark so called model views; both auxiliary and master view. The Master view (marked by ‘M’) is the original model and the auxiliary view(s) are copies (re-used elements) of a model and have an ‘a’ indicator.
When you copy a model element then VP creates a new view by default, I think that might be the reason these got created.
The purpose is to allow you to re-use a model element (and all its attached meta-data) and keep that accessible and manageable. So: if you need to change any meta-data (for example the description or maybe a reference) then this change will be applied to all elements at once.
You can turn these indicators on and off by using the “Model Indicator” option in the view tab.
Hope this helps!