Open Task Columns dialog (e.g. by clicking a cog icon in the task table)
Create a custom column with the name and type matching one of the existing built-in columns, e.g. Duration (note: perhaps it makes sense to show a warning in such case, because columns with the same name may trigger other problems)
Click "Apply"
Expected: there is a single new custom column with "Duration" name
Actual: there are two "Duration" columns
If you delete one of the two Duration columns in the column list in "Task Columns" dialog, both will be deleted.
Scenario:
Expected: there is a single new custom column with "Duration" name Actual: there are two "Duration" columns
If you delete one of the two Duration columns in the column list in "Task Columns" dialog, both will be deleted.