The Bug:

minecraft.used:minecraft.COMPOSTABLE_ITEM doesn't increase when placing an item into a composter.

Steps to Reproduce:

• Create a scoreboard objective for tracking the use of any compostable item and set it to display on the sidebar.

/scoreboard objectives add UseAzalea minecraft.used:minecraft.azalea
/scoreboard objectives setdisplay sidebar UseAzalea

• Right-click on a composter whilst holding the compostable item of your choice.
  →  Notice how the scoreboard doesn't increase despite the item being used.