Introduce drag and drop feature (in bulk) for converting features into master features or mater features into regular features. This will save time and allow bulk actions for imported data and when manipulating multiple feature cards in correct hierarchy.
Thank you for your idea. While it does not use drag and drop, converting features to epics (and vice versa) in bulk is currently possible using bulk edit. From a list report, select the records you wish to convert, click Bulk edit, and select the Convert to option.