(on going edits)
Wizard 20 can make :
9 glyph slot = 8 spell
7 glyph slot = 7 spell
6 glyph slot = 6 spell
5 glyph slot = 5 spell
5 glyph slot = 4 spell
4 glyph slot = 4 spell
3 glyph slot = 2 spell
3 glyph slot = 2 spell
3 glyph slot = 2 spell
Wiz 20 "slot" = 3 spell (1 or 2)
short rest
5 glyph slot = 5 spell (recovery)
Wiz 20 "slot" = 3 spell (1 or 2)
... so that's 14 per day with 1 short rest.
At level 18 you could use all of the Glyph slots, on the spammed 1 and/or 2
but that's kinda "iffy" tactics and you'd run out of daylight to do all of it anyway.
Variants :
Could use the Glyph 8 slot , to cast Wish , which makes up to an 8 , and it's that 8 that goes into the Glyph.
Cleric 20 misses out on a 5(+), but has a DMother-may-I chance at an extra 9 slot, to make a 9 Glyph.
Making all the Glyphs out of Rituals, ~doubles the # of glyphs, but is Obviously
"iffy" tactics, and is competing with going the Wiz 18 spam for each glyph slot.
Cleric Arcana 20, could check dmother-may-i first, then do the 8-wish-8 trick (if dm).
edit --- added Wiz 20 into the mix recounted, changed stupid to "iffy", Cleric Arcana.