Is there a possibility to edit entries of the elements of the Entity Relation category? E.g. If I want to change name and properties of Entity Extended.The only thing I can do is to add text below the box OR edit the xml manually.
You can change the text value in the style (Edit->Edit Style) of a selected cell to input the text you want, see this slightly out of date video. We will add it to the right click menu, but we can't give a date currently.
Note, you can also press cmd/ctrl + E to bring up the style dialog.