As it stands now, if you use a Glyph or Rune on an item, then close the Forge, reopen it and put a new item in it, the Glyph or Rune from previous crafting remains in place. Runes aren’t a big deal because you see Shatter, Remove An Affix, etc at the bottom, but I’ve wasted many a Glyph of the Guardian because it’s stayed in place when crafting a new item when I did not need it (crafting on 1 Instability items for example).
I think on a NEW forge ‘instance’ it should reset everything. If you keep the forge open to shatter a bunch of items for example, it should keep your Rune of Shattering in place. But if you close the forge and reopen it, have it reset all Glyphs and Runes.