You can export the dimensions fields and edit them in a bulk file.
Here are the steps:
1- Select the products and go to Export>Dimensions.
2- Download the file from the Notifications from the top right.
These are the fields in the file.
IMPORTANT NOTE: If you want to delete a specific field data, you must leave the cells as empty. This action will delete the data which you have already in SA, when you upload the file back into SA.
3- After the changes, upload the file back into SA.