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It could be useful to have set a shortcut to specific activity. For examples gesture/shortcut to ran web browser will start Firefox with developer profile on Web Creation activity, but movie watching Firefox profile on entertainment activity.

Update:
Other use cases:
1. Imagine I'm photographer and developer and have hobby/photography and work/development activities. I add super+e to hobby activity to open dolphin with images directory and super+e to open dolphin ~/work directory. In the same time I have super+m (m mean main) to open kdevelop on work activity and super+m to open digikam on hobby activity.