There are several issues found with the environment UI.

1.

Cannot disable the variable in the first item with the "Disable" button.

Any item but the first can be disabled with the button and are shown crossed out with the raw code showing a "#" has been added to the start of the line statement.

Manually adding a "#" to the first item's line statement will show that the item is crossed out.

2.

Pressing the "Edit" button when selecting a disabled item will add a new item and line.