Maybe, I found RC11 bug.
When I enable “Show Line Numbers”(in Janapnese, “行番号を表示”), The edit area becomes too narrow, and left side are hidden.
Note: I’m using Scrivener3 RC11 Windows on Japanese environment.
This issue is still present in RC13 (version 184.108.40.206 Beta (1129554) 64-bit).
When I activate the “View > Text Editing > Show Line Numbers” option, the first character of each line is hidden by the vertical grey line-numbering overlay - see attached screenshot.
[attachment=0]Show Line Numbers Issue - Screenshot 20201209.jpg[/attachment]
Thanks, I have updated our bug tracking system. A temporary workaround is to increase your left/right editor margins.