Not being able to edit 'staff text line' or 'system text line'
S3 - Major
So when you add an 'system text' or 'staff text' you're allowed to edit this by double clicking the item. You can add your own text. But for both 'system text line' and 'staff text line' from the Text Palette there's no option or way to edit this text. Meaning this function is broken.
I can edit the text easily enough in the various lines (including staff text, system text, voltas, cresc., and dim.) - the properties have two option boxes: "Style" and "Text". Selecting the "Text" box allows editing the text. However, I found no method to change the text style as can be done with staff text and system text. In one of my scores, the arranger, wanted "Build", underlined, instead of "cresc.". I found no way to add the underline.
To keep with the smaller size of the properties in MU 4.0, one implementation, would be to provide a third box, in addition to the line style and the text option boxes, possibly called "Text Style". Another would be to provide a "more" pop-up for each text option (beginning, continuation, end as appropriate) to allow changing the text style.