Shadow as an idea or a real thing is used in the Bible and literature, especially poetry, as a metaphor. In Psalms, we may “hide (or rest) in the shadow of the Almighty” and know we are protected, or the Law and the earthly Ark are but shadows of better things (Hebrews). So, when you read passages and stories you have to read things in the context of what the writer is saying.
Good or Bad
Like knowledge or wine/grapes, a shadow may be a good thing or a bad thing. We can hide in the shadow of God’s wings, or someone can shoot arrows at us from the shadows (hiding). In the Lord of the Rings, Frodo was passing into the shadows or shadowland after he was stabbed. On a hot day, who does not like to sit in the shadow (shade) of a tree or umbrella?
Luke 13:19 is the story of a mustard seed (Kingdom of God) growing into a tree and birds using its shade (shadow) to nest in. In this story, the shade is good because it represents the Kingdom, but those birds (usually a metaphor for bad things) are taking advantage of the Kingdom and raising things that will just use the Kingdom.
Moses, David, and Jesus (the Holy Spirit) all used shadow as a metaphor in their teachings and writings; it has been around for a very long time. (Use the sites below as a learning tool, I did. I just may not agree with everything they wrote.) I enjoy looking at the roots and early thoughts of words and ideas, it is how our “box” was formed so we can think outside of it.
A shadow is a place of separation. It can separate light from dark and thus became a divider for good and evil. The shade also becomes a symbol of protection because of His hand, wings, or Himself.
In the NIV shadow is used in forty-four verses, some things the KJV (60+ times) would call shadow, it uses darkness. Other translations have varying numbers of verses that use shadow. To be fair you might have to search shade or even cover to find verses that you want.