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

OpenShot Video Editor is a free and open-source video editor for Windows, macOS, Linux, and Chrome OS. The project started in August 2008 by Jonathan Thomas, with the objective of providing a stable, free, and friendly to use video editor.
The program supports Windows, macOS, and Linux ever since version 2.1.0 (released in 2016).OpenShot added support for Chrome OS in version 2.6.0 (released in 2021). There is an unofficial portable version beginning in 2020.
OpenShot is written in Python, PyQt5, C++ and offers a Python API.[12] OpenShot’s core video editing functionality is implemented in a C++ library, libopenshot. The core audio editing is based on the JUCE librar
Features
Cross-platform video editing software (Linux, macOS, Windows and Chrome OS).
Support for many video, audio, and image formats using the FFmpeg library. For a full list of supported formats, see the FFmpeg project.
Powerful curve-based Key frame animations OpenShot comes with a powerful key frame animation framework, capable of an unlimited number of key frames and animation possibilities. Key frames interpolation mode can be quadratic bezier curves, linear, or constant, which determines how the animated values are calculated.
Desktop integration (drag and drop support, native file browsers, window borders).
Unlimited tracks / layers Tracks are used to layer images, videos, and audio in a project. You can create as many layers as needed, such as watermarks, background audio tracks, background videos, etc… Any transparency will show through the layer below it. Tracks can also be moved up, down, or locked.
Clip resizing, scaling, trimming, snapping, rotation, cutting, alpha, and adjusting X,Y location. These properties can also be animated over time with just a few clicks! You can also use our transform tool to interactively resize clips.
Video transitions with real-time previews Over 400 transitions are included in OpenShot, which lets you gradually fade from one clip to another. The quickness and sharpness of the transitions can also be adjusted using keyframes (if needed). Overlapping two clips will create a new transition automatically.
Compositing, image overlays, watermarks When arranging clips in a video project, images on the higher tracks/layers will be displayed on top, and the lower tracks will be displayed behind them. Much like a stack of paper, items on top cover up items below them. And if you cut any holes out (i.e. transparency) the lower images will show though.
Title templates, title creation, sub-titles Over 40 vector title templates are included with OpenShot, which makes adding titles to your project fun and easy. You can also create your own SVG vector titles, and use those as templates instead. Quickly adjust the font, color, and text of your titles in our built-in title editor.
3D animated titles (and effects) using Blender.
Advanced Timeline, with features including: Drag & drop, scrolling, alignment, panning, zooming, slicing, preset animation and settings, etc.
Frame accuracy (step through each frame of video) Our video editing library (libopenshot) has been built with accuracy in mind. This allows OpenShot to finely adjust which frames are shown (and when). Use the arrow keys on your keyboard to step frame by frame through your video project.
Time-mapping and speed changes on clips (slow/fast, forward/backward, etc…) Control the power of time with OpenShot! Speed up and slow down clips. Reverse the direction of a video. Or manually animate the speed and direction of your clip as you wish, using the key frame animation system.
Audio mixing and editing features, such as displaying waveforms on the timeline, or even rendering the waveform as part of your video. You can also split the audio from your video clip, and adjust each audio channel individually.
Digital video effects, including brightness, gamma, hue, greyscale, chroma key (bluescreen / greenscreen) OpenShot includes many video effects (with more on the way). OpenShot allows you to adjust brightness, gamma, hue, greyscale, chroma key, and more.