There are a few things which to me behave in an unexpected way or seem inconvenient:

1. After applying a main color and accent color to a paintbrush, there doesn't seem to be any way to "reset" the brush (clicking on a cauldron with water does not work). This becomes an issue when you want to only apply an accent color to barrels but the brush has a main color which there is no obvious way to clear, because setting the color to "No Color" doesn't seem to work. The only way I have found to clear the colors is apply a material to a brush, and then apply the color I want.
2. I'm not sure if it is possible to remove decorations from a storage block that is already placed down, I think it would be good if I would be able to do this somehow.
3. I noticed that shulker boxes cannot be decorated with a material. Is this an intentional limitation?