We understand your question about whether recording dreams is a sin, and we appreciate your desire to seek what honors God in this area.
We agree that the act of simply writing down or recording dreams is not in itself forbidden in Scripture. God has at times used dreams to reveal His purposes, as we see with Joseph in Genesis 37:5 and Genesis 40:8 and with Daniel in Daniel 1:17 and Daniel 2:28, and the Lord says in Numbers 12:6 and Job 33:15 that He has spoken in dreams. The Bible also says in Joel 2:28 that your old men shall dream dreams, which is quoted in Acts 2:17. So we do not rebuke the neutral discipline of noting what you have dreamed for the sake of reflection or creativity.
At the same time we want to lovingly caution you, because intent and practice do matter. Scripture clearly forbids divination, interpreting omens, and seeking hidden knowledge apart from God in Deuteronomy 18:10-12, and we are told in Jeremiah 23:28 and Ecclesiastes 5:7 not to give undue weight to dreams. In the examples of Joseph and Daniel, it was God who gave both the dream and the interpretation, not a technique or a mystical method. Dreams were never to replace the revealed Word of God. We are taught in Hebrews 1:1-2 that in these last days God has spoken to us by His Son, and in 2 Timothy 3:16-17 and Psalm 119:105 that Scripture is sufficient and is a lamp to our feet. If dream recording becomes an obsession, leads to fear or anxiety, causes you to seek guidance from dreams more than from Scripture and prayer, or moves into seeking meaning through occult, New Age, or divination practices, then it does become spiritually harmful and should be repented of and turned away from. We are called to test all things in 1 John 4:1 and to trust in the Lord with all our heart and not lean on our own understanding in Proverbs 3:5-6.
So we would encourage you if you choose to record dreams to do so with a heart focused on Christ, bringing anything that seems significant before the Lord in prayer, comparing it to Scripture, and asking for wisdom which God gives liberally in James 1:5, without elevating any dream above the Bible or using it as a form of fortune telling.
We also noticed your question did not mention Jesus Christ, and we want to gently remind you that it is only through Him that we have access to God. In John 14:6 Jesus said He is the way, the truth, and the life and no one comes to the Father except through Him, and in Acts 4:12 there is no other name under heaven by which we must be saved. If you have not already, we encourage you to put your faith in Jesus, believing He died for your sins and rose again, and to call upon His name for salvation in Romans 10:9-13.
We pray together for you now. Father, we come before You in the name of Jesus Christ and thank You for this one who desires to honor You. We ask for wisdom and discernment, that You would guard their heart and mind from deception and from any practice that would draw them away from Your Word. Help them to keep Scripture as their final authority and to seek You first in prayer. If any pattern in dreams is from You, make it clear according to Your will, and if not, give peace to release it. Draw them closer to Jesus and let Your Holy Spirit guide them into all truth. We ask this in Jesus name, amen.