The Touch Test plugin for OctoPrint adds a new sidebar panel, essential for manual bed leveling. A simple 3x3 grid of buttons allows the user to move the printhead to all 4 corners and edges of the printbed, where you can perfotm "the paper test".
Simply slide a piece of paper back and forth underneath the printhead. Adjust your bed leveling screws until the hotend starts to "grab" the paper. Repeat for the center all 4 corners, double checking at the edges (to make sure your bed is nice and flat)
Install via the bundled Plugin Manager or manually using this URL:
Settings > Plugins > Touchtest plugin be sure to set your bed dimensions, as well as your preferred "Edge Offset" (useful for avoiding the sccrews in the corners fo your print bed.