How to create a video sequence using vertical 9:16 video clips.

Olive is a free and open-source cross-platform video editing application for Linux, Windows and macOS. It is currently in alpha.
It is released under GNU General Public License version 3. It is written in C++ and uses Qt for its graphical user interface, FFmpeg for its multimedia functions, OpenImageIO library, OpenColorIO for color management and CMake build system for configuring.
The plan of the development team is to combine complete color management, a fast and high-fidelity half-float/float-based render pipeline, node-based compositing and audio mixing, and a highly efficient automated disk cache all together in the one program. According to the development team, this batch of features is one “no other NLE – not even commercial – has tried to do”.