Currently, the only way for users to add columns is to Open Advanced Find (which moves them out of Unified Interface) and use the very old and cumbersome way to add a column to a view which is not intuitive (e.g. rearranging, resizing takes multiple attempts before it looks right). Especially for ad-hoc adjustments (e.g. I quickly want to add one more column, just temporarily) this is cumbersome and not intuitive. The new view editor in PowerApps is nice, but only available for Admins.
Please add a feature to add columns ad-hoc to any view and to rearrange them. If the user made a change, add the same asterisk (*) to the view name (the same way it is added when the user changes the filters in the new filter pane). Then allow users to save the changed columns and filters as a new view from the ribbon via "Save as new view" command.
Together with the new filter pane, this would eliminate the need for Advanced Find and provide a more streamlined unified interface experience. See quick mockup below.