Is all graph text editable?

Yes. There are two different types of text in graphs. The first is normal editable text that you can change in the Graph Titles/Text dialog (e.g., by double-clicking on a title). The second is text that is automatically created and updated by STATISTICA, (e.g., graph legends, functions, statistics). This second type of text (and/or symbols) consists of separate "active objects" (e.g., the point marker symbol in a legend) that are automatically updated by STATISTICA. You can always insert new text in between active objects. Note that you can also selectively disconnect any active object from auto updating and therefore be able to edit it (but, of course, lose the auto-updating feature) by right-clicking on it and selecting Disconnect Object(s) from Graph from the resulting shortcut menu.