(Odo v18) If you are looking to duplicate the worksheet template of field service directly, this may not be a direct option since wokrsheet templates in field service are designed with studio fields, usually the duplicate action works with records which has same prestablished fields, but when you set a new worksheet there are no predetermined fields to use.

There is an alternative which is going to Settings > Technical > Database Structure > Models and then exporting the workshet with all the fields and then importing in an empty newly creadted workshet model, as a plus you can keep the xls files as a support if you wish to duplicate new worksheet for modifications.