Here's information on how to merge SKUs in the ERP module.
If you have accidentally created duplicate SKUs (e.g. pants-black-XS and pants -black-XS with a space in the SKU), you can easily merge them and the system will do the rest of the work in merging product history, etc.
Go to Admin Tools > Utility > Merge SKUs.
Then either by typing them in or using the Search function, enter in the SKU you want to change and the SKU you want it to merge with. Click Apply.
You will see a notification letting you know the merge was successful.
Warning: At this time, you can ONLY merge at the SKU level (individual product). You cannot merge Styles or Substyles. Attempting to do so will cause the system to error and your child SKUs to disappear. It is important to only merge SKUs.