How to get current list of decorations OR handle decoration position change in VSCode Extension?

Lets take this example into account.
I have a file with contents:

  1: one
  2: two
  3: three

and I create a line decoration for line "two":

const position = new vscode.Position(1, 0);
const range = new vscode.Range(position, position);

const decoration = vscode.window.createTextEditorDecorationType({
  gutterIconPath: context.asAbsolutePath('images/icon.svg')
});

vscode.window.activeTextEditor?.setDecorations(decoration, [range]);

that gives me

  1: one
* 2: two
  3: three

Next step: I am changing file contents by adding a new line before line "two".
After that file looks like this:

  1: one
  2: 
* 3: two
  4: three

As you can see VSCode has updated my line decoration and now it is positioned on line 3 (instead of 2) which is totally correct and I've expected that.

And now the question: how can I get this current updated position of my line decoration? If I hold the range reference - it is still pointing to line 2.

What is the right way to handle this decoration changes?

Either of these 2 options would satisfy me:

1. a way to query all the current decoration positions displayed for currently open file
2. a way to subscribe to decoration / range changes so that I can handle those manually.

Maybe I am totally wrong and it should be done in another way.
Please advise!