I deleted several variations of a product and when I manually added the variations back, the original orders were not linked to the new variations even though I added the same sku. Can it relink to the original order?
Unfortunately, I do not think that can be done. They are most likely linked with what is called a GLOBAL ID. In this case, it would look like this:
gid://shopify/ProductVariant/123
The issue is when you delete a variation and create a new one, it deletes the GID and creates a new GID. That GID is what links the variation to the order. There is just no way to accomplish this task, unfortunately. For future reference, if you are concerned about this for a certain variation, I would just edit the variation and it will then keep the product linked to past orders.