Rename Google Doc
In Google Docs, Sheets and Slides on a mobile device it is easy to set the document name. By default the document title is “Untitled Document.” Even if you do not rename the file, the “Untitled Document” will save edits.
Google Docs App
More Options Icon
The more options icon (3 dots) in the upper right allows you to name the document. Click on the 3 dots.