How can I set default columns for all my users in the List View?
When creating a filter in the List View of Pipedrive, you may choose the 'Save selected columns with the filter' option in the Create new filter prompt.
When the saved filter is selected, the columns used when the filter was saved will be used to display the filter results. In this way, your users may all use the same filter, and will then be shown the same column headers in the List View.
If you wish for a filter to be viewable by other users in your Pipedrive account, be sure to set the visibility of the saved filter as Shared.