A slow procession is read as a collective farewell to something that has ended. Walking in it suggests accepting the ending; watching from aside, keeping some distance from the grief.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.