The default Ubuntu 18.04 Dash-to-dock dock allows a thumbnail preview of open windows for an application. You initiate this by hovering over the application and clicking once on it. There's no point requiring a click, and I'd rather the sequence initiate simply by hovering over the program (something Windows 7/10 actually gets right).
This is already offered by Dash-to-panel as demonstrated here. But Dash-to-panel can't be placed on the left side of the screen where I need it. Only options for Dash-to-panel are bottom or top of screen.
How do I turn on this Dash-to-dock hover preview that I want?
This is currently not possible as such in Dash to Dock. It would need to be implemented as a feature in future versions. It appears as if there is work being done on this, so this may be implemented soon in a new version of Dash to Dock.