So that could be by upgrading runes already in an item or crafting unset runes in a device with reagents or multiples of the same rune combining to ‘upgrade’ the rune.
Blizzard also appears to be using the same names and some of the visual representations of the rune symbols as seen in Diablo 2. It’s unclear if all the 33 different runes from Diablo 2 will be the same in Diablo 4. However, some have been identifies as shown in the list below.
Some of the Diablo 4 runes have been confirmed already but note, the socketed properties in Diablo 4 are different from the properties in Diablo 2. Below is a list of all the expected runes based on the Diablo 2 runes. The list shows confirmed runes for Diablo IV and their new properties.