If you accidentally cut an extension cord, your first instinct may be to just throw it out. But, it is possible to salvage the remains for a functional cord. You might think to splice the ends of the cut cord together, but this is not permissible under the National Electric Code, due to the damaged abrasion resistance.
Instead, you can use the separate parts to make new extension cords, so long as the pieces are long enough. You can purchase a high quality receptacle and plug and attach it to the ends of your cut wire. You’ll want to ensure that new parts have built-in strain relief clamps and can carry the same load as the previous wire.
If one of the ends is so short that it’s not worth saving, then you can throw that piece out and save the other end. Since extension cords can be expensive, this option is preferable to having to buy a completely new cord.