How do you adjust the speed of the seekbar?
The seekbar's overall time is set by the elements on the slide such as audio, video, etc. or if there is no media elements it's set at the default slide length. The slide duration can be controlled as described here.
Could you please take the following idea forwards to your team. https://community.articulate.com/discussions/articulate-storyline/ability-to-change-storyline-play-speed#reply-331728
This would make a huge difference to the software in teaching settings. As this kind of software tool is used more and more it would be an asset to secure for the future.
I certainly can and you can also share ideas and specific requests with our team directly by sending them along in the form of a feature request here.
If we can assist you with anything else, please feel free to let us know!