When you’re entering or placing text in a text frame in your document, InDesign lets you know when you have more text than it is able to display in the frame by adding a tiny red + icon in the lower right corner of the frame indicating overset text. For obvious reasons, you might want to know how much text is overset, but expanding the frame to see how much text is overset is, well, overkill.
Instead, you can view exactly what text is overset by simply hitting Command + Y with the text frame selected. This brings up a small window called the Story Editor.
At the bottom, you’ll see a red bar along the side, as well as a gray divider line showing exactly how much text is overset. To save time, you can edit your text right in the Story Editor until it all fits in the frame, if that’s what you choose to do.