Dubb allows you to automatically generate an SRT file, or transcription, of your video.
You must be enrolled in a Caption Plan
To edit the captions, download the SRT file, use the Text Edit app for Mac or Notepad for Windows to edit, once you're done, save, and then re-upload the file.
You can also upload existing SRT files from other sources
Here are videos for how to generate the SRT files on Dubb, and the second video shows how you can do so on Youtube.
If you need to remove captions you uploaded on Dubb, you can remove the SRT file.