I’ve created another web app. This one allows map visualisation and editing.
You can access it here - https://mapeditor.myecu.biz/
Let me know if you have any issues or would like extra features

First select the map you want to edit.
You can then press InDur or SpkAdv to display a grid and a chart.
Use the left mouse button to select a rectangle in the grid. Then use the % adjustment buttons below the grid.
Finally use Save File to download the updated map.

I'll see how easy that is. You can hover over a point to get some info.

FYI - the initial framework of showing the grid and chart and selecting was done by chatGPT. I then added the map parsing and adjustment code.