Hi Chendo
We have experienced a similar issue. Instead of setting everything to empty, we wrote some logic in the after startup action that loops over all the accounts and their column configurations. Within the loop, we change the JSON to capture the changes that we made. For example when adding a column, we agreed that it would always appear at the end of the grid, so it is as simple to append the new JSON object at the end of the string.
For changing column numbers and removing columns, it gets a bit more complex in your logic (changing all column numbers +1 or -1), however if your logic works, it should just get the job done.
It is a bit cumbersome, I admit, but it works if you add the logic in the right way.
I hope this helps.
Very unstable, this should be inbuilt in the widget, lots of custom logic for a simple feature.
Just noticed that Mendix released a new version of the Data Widgets (v2.12.1) where the issue is 'fixed'. (Since v.12.0)
The fix Mendix built in is that it cleans the configuration and that it's set to empty again when there is a change on the columns...