It may happen that you have text frames on an InDesign page, that are not linked to any articles, but contain some text.

The Select First Import command (Plug-Ins menu, GN4, Utilities) allows you to quickly identify such frames.

It scans all the frames on the page in the same order they were created drawn and selects and brings into the window focus the first one that contains some text and it is not marked as Disable Import.

Then, in the second step, you can import them into GN4 via the Plug-Ins>GN4 Add to Article or Create New Article/Img commands.

Repeat the command to locate the next importable but not imported frame, until the command displays the information that "There are no items that need to be imported into GN4".

Select First Import command and empty text frames

If the text frames are empty, even if you marked them with the appropriate GN4 type, the Select First Import command won't select them.