If you'd like to create a new segment in Funnel that's similar to one of your existing segments, simply navigate to the segment and then click the 'copy' icon at the top-right hand side.

Once you click the 'copy' icon, you'll be prompted to rename your new segment.

After you've renamed the segment, click 'create segment' and then you'll be taken to the segment view. 

From here, you can click on the existing conditions and make any edits that you wish – these changes will be reflected in your new segment automatically.