There are a decent amount of effects you can achieve through Glyphs, but there can always be more!
Whether it's something useful or something just for fun (and at the risk of diluting the pool of Glyph effects...), there could always stand to be some more possible Glyph effects.
Now, I can't think of everything, but here's a few ideas:
Glyph of Massiveness- Increases the character's model size
Shrinking Glyph- Decreases the character's model size
These effects would probably be cast-on-self, and affect the character's height, sort of like you can see in some miscellaneous instances in the game, like failing a Freestyle Jam, or a Mini Potion, or other such things.
Some other silly visual effects could be kind of fun.
Glyph of Afterimages- Leave behind after images occasionally, similar to the effect you get when teleporting using stuff like Final Hit/Final Shot
Sulfurous Glyph- Appear to be Sulfur Poisoned
Toxic Glyph- Appear to be Poisoned
They're not useful, but just for fun similar to the Suspicious Whispers effect, so at least there's a precedent for these kinds of effects.
Then some other things, like affecting life skills maybe
Glyph of Mastercraft- Increases Production Quality
Glyphs for Blacksmithing/Tailoring/Handicraft/Weaving/etc Success Rate- Increase success rate of the relevant skill
Gatherer's Bounty Glyph- Increases Chance of gathering an additional item
Speedy Gatherer Glyph- Decrease gathering time
Gatherer's Eye Glyph- Increase Gathering Success Rate
The gathering effects would be similar to the reforge effects of gathering speed/bonus chance, but I decided to make them general rather than make individual glyphs for, like, Mushroom Gathering or Hoeing.
Then I went in the opposite direction with the production success rate glyphs. Since the reforge-counterparts are skill-specific, I kinda went with that.
Though I do think making THOSE general as well would help mitigate the dilution of possible glyph effects. (The RNG of Formulating effects needs all the help it can get, after all)
The quality glyph is a bit of a tossup. There's a reforge effect for Tailoring, but not Blacksmithing, and Carpentry has both Min/Max Quality reforge effects, and then the weirdness that is the random rolls of MC/Engi. My idea is just a general Quality Up, similar to the enchant, but eh...
Anyways, I just thought it was a bit weird that life skills were seemingly left out almost entirely of Glyph effects.
And I guess if there are useless effects like Meditation Regen Rate Increase, there could also be dumb life skill glyph effects, just to round out the pool of useless effects for Life Skill Glyphs. Maybe like Rest Effect Up or Campfire Duration or something. (or we could just prune such useless "useful" effects altogether. Who would use a Meditation Up glyph when they could just use a place-on-ground MP recovery glyph that can affect you AND party members)
Well, I can't think of everything, and I'm not sure if all my ideas hold water, so list some of your own ideas for glyph effects!
Fun effects, useful effects, whichever! I just feel that Glyphs could use a bit... more!