Delete Phone/Tablet Steps

We need to update all our instructions with new txt/label style and there is a problem. Some projects, the early ones had some phone adjusted steps. So…after update it looks good on pc, when viewed on phone, those old 2d objects remain along with the new ones. Is there a way to delete those Phone/tablet adjusted steps? Please tell me that is a solution because this is of huge importance for us.
Thank You.