The sequencer won't show up every time Uunreal launches

Every time I open Unreal, the setting isn’t the same I saved. Say, I hid two characters and left a single character on the scene and was working on animation with the sequencer. Saved and went to bed.
Next day, when I open it, the all characters show up and the sequencer disappears. I lost everything what I did last night. Thus, I have to start over. It’s frustrating.
How do I fix it?