sigils transformation

Might be stupid question but in version 2.3 how can I transform small sigils into major sigils? I thought that is possible? Now I just don’t see a way…

You can transform 3 cores into a Minor Sigil, but the only way to acquire a Major Sigil is to either find them through looting, or by clearing a Minor Sigil.

Oh so I remembered something wrong. Thank you for the fast answer.