Questions about Numberred Lines (issue #3917)

Hello, I am new to this open-source project. I am currently trying to figure out what part in the source code went wrong. My first guess is somewhere at packages/app-desktop/gui/NoteEditor or packages/app-desktop/gui/TinyMCE, I appreciate any suggestions or tips on reading and understanding the source code. Here is a link to the issue, Thanks!

Based on the description in the issue, it looks like the issue is using the CodeMirror markdown editor. I took a look and the relevant lines are here

Thanks! I would mess around on my local branch!