In 1.14.4, each small flower/plant has an associated effect. These effects can be applied to the player if they eat a Suspicious Stew made with that plant. Currently, no vanilla flower grants Invisibility. I feel that Invisibility (alternatively, but less useful, glowing) would be a good fit for Faint Amaranth, if someone attempted to put it in their stew.

Small flowers can craft stews, and are in the tag minecraft:small_flowers.

Further reading:
https://mcreator.net/forum/55774/tutorial-custom-suspicious-stews-114
https://minecraft.gamepedia.com/Suspicious_Stew