JSON Commenter is a vscode extension that lets you create inline comments in a JSON file while keeping valid syntax. You create a block with a command that places the comment anywhere legal in the JSON. The text is edited inline and supports word wrap, padding, margins, etc.

The comment is in a somewhat good-looking box with minimal extra characters. Zero-width unicode chars give keys that only show two quotes. This is a sample comment block...

  "         ":"----------------------",
  "         ":" This is a comment.   ",
  "         ":"----------------------",