I know you can make stuff transparent but scratch doesn't already have opacity on the drawing tool and over it be pretty helpful

i am pretty sure, if you are on pc or sum, you can download some mods that contain a opacity tool

You could use ghost effect.

To make transparent sprites you have two options:

Use an external website such as TurboWarp and use the opacity tool over there

Use the ghost effect that will make the sprite transparent over time.

Ghost effect is generally more useful for transitions while the Opacity Tool helps whenever you want only part of the sprite to be transparent

use that extension