Summary
When creating a new Level Sequence in UEFN, the Sequencer window is completely blank except for the toolbar options. The +Track button, tracks, and timeline are all missing.
[Update] Solution
I had a friend export their Level Sequence settings and share with me. After importing settings and restarting, the Sequencer window returned. I’ve never made changes to Level Sequence settings but somehow they were changed. I find it curious that settings cannot be reset to defaults.