I've had this problem before and can't remember how I solved it. I run a dual vertical lister and I have removed columns in each pane that I don't want to see and have saved this as my default.
However when I close and re-open DO, one column keeps re-appearing: Availability. I've looked at the v12 FAQ and done what it says (i.e. saved & cleared formats) but this Availability column insists on re-appearing.
I can use the padlock on each pane but the FAQ says that this isn't the best solution.
The columns that I want displayed and that seem to stick ok are:
How can I stop Availability from displaying?