Is it possible to show hidden characters on a Google Doc? If not, how does one request such a feature?
Currently, no. Source.
This seems to be the place to send Google your feedback with regards to Google Drive. Here is a filtered view of the Google Docs help page which you may want to try posting your feedback in as well.
There is now a way. Show is an extension that displays non-printable characters within a Google Docs document.
2If you are affiliated with the creator of the extension, you should disclose it. Mar 9, 2017 at 12:27
3What about Sebastien's comment makes you think he's affiliated with the creator???– bobpaulFeb 19, 2018 at 21:20
Found in a more recent forum that there's an add-on called Show that works, so you can see non-printable characters in your Google Doc.