Version 4.2.0.16.356
In the Format: Advanced Format screen there is a possibility to adapt the sample plsql code by editing the text.
When typing in a new line of source, a pop-up window shows up with Syntax Error at line .... It is clear that there is a syntax error, since I am still tying in a new statement. Now you have to click the ok button of the window before tying ahead. And the pop-up keeps on appearing till you click the close button (X right top).
Better is to show the text in text field at the bottom of the Advanced Format window.
Further the changes are not marked in green (as Jeff as described)