Dynamic Site Data Value Editing

On a dynamic website there are several numerical figures displayed to the user—think scores, counters and live totals—that I need to change quickly and reliably without touching the rest of the page. I do not mind whether you manipulate the DOM directly, inject a short JavaScript snippet, create a browser userscript or build a lightweight admin endpoint; use whichever method you are most comfortable with so long as it works every time the page reloads.

The task is straightforward:
1. Identify the current elements where those numbers live.
2. Provide a clean, reproducible way for me to update them on demand (no hard-refresh edits).
3. Leave the rest of the site’s dynamic behaviour intact.

Please deliver:
• A concise piece of code or tool with clear usage instructions.
• A quick read-me that shows how to plug it into the existing environment and how to change the values going forward.
• A brief test confirming that the edited numbers persist through typical user navigation.

If jQuery, vanilla JavaScript, userscripts, or even a small backend endpoint suits you, that’s fine; I care about reliability and ease of use more than the specific stack.