Task Container / Focus Session (like in the new Trello update)

I would love to create an event in my calendar where I can add my tasks—similar to the new Trello update (see picture). For example, I could create a focus session or a session dedicated to a specific project. It would be great to name the event freely, just like a regular calendar entry. Then, I could drag and drop the to-dos from my list into the event—either to plan what I want to accomplish during that time frame or to track which tasks I completed in that period.