Was not the design of putting the altar before the vail of the mercy-seat to show that Jesus is always appearing in the presence of God for his people? Hebrews 9:24-26.
Related Commentaries of Exodus 30:5
Exodus 30:5-6
5 And thou shalt make the staves of shittim wood, and overlay them with gold.
6 And thou shalt put it before the vail that is by the ark of the testimony, before the mercy seat that is over the testimony, where I will meet with thee.