Listings that have variations and are posted on eBay, have limited access to them which means you can only add/remove variations or change quantity and price without having to end the listing.
If you would like to edit the Variation SKUs, or variable values for the Live listing, then you will have to open eBay and search for the product you want to edit and make the changes directly on eBay.
After you are done, save the changes on eBay and then go back to Ad-Lister and select the listing (from the Listing page) and in the Action dropdown, you use the Reimport option to import the changes back into Ad-Lister.
If you would like to import the changed variations back into Ad-Lister for only one product, you can Retrieve the variations from eBay directly on the Variations page in Ad-Lister.