This is only possible in the web browser version. Please refer to the manual for detailed operation instructions.
Remove parts of video (Web Browser)
https://teachme.jp/8/manuals/14366649
For other apps, you can consider preparing the video file and extracting only the necessary parts as multiple videos. However, you cannot combine the extracted videos into one video.
Extract image or video clip from video file (Mobile App)
https://teachme.jp/8/manuals/3741955
If you want to perform more complex video editing, please edit the video using other video editing apps (software) and then upload it to Teachme Biz.
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Related: Can I cut unnecessary parts from the beginning or end of a video?
https://help.teachme.jp/hc/en-us/articles/900005510506