TROUBLESHOOT
VOCALOID3 Editor
Make the mixer window floating (this can be set as follows: "Settings" menu -> "Preferences" -> "View Settings" tab -> "Mixer" section). Then, in the "Window" menu, select "Tile Horizontally" to align "Track Editor", "Musical Editor", and "VOCALOID MIXER" on the display.
If you are unable to find a solution in the Troubleshooting section, please use the Inquiry Form to submit an inquiry.