There is only one file type that uses the .MEPX extension:
Movavi Video Editor Project
A MEPX file is a Movavi Video Editor Project. It organizes and links to the media files included in a Movavi video project. MEPX files can be exported from Movavi Video Editor as .MP4, .AVI, .MOV, and other types of files, for use with media players and other devices.
MEPX files can be opened only using Movavi Video Editor or another Movavi video editing application. To open a MEPX file in Movavi Video Editor, selectfrom the program's menu bar. Then, locate and open your MEPX file.
Updated: June 9, 2020