I made a few rather fundamental changes to Preferences / Add your own columns. If you run from source then please post here if you find things that don't work.
Some of the changes:
- Added a column showing the status of the column: edited, new, deleted.
- You can undelete a deleted column if you haven't accepted the changes.
- You can't reuse a lookup name until the changes have been accepted. This was the bug that started the process.
- Added tooltips to show the contents of the cells when the columns are narrow.
- Some improvement in error handling.