I was working on a part yesterday in "Sheet Metal Design", and I am trying to open the part so I can continue working on it today, whenever I open the part, it opens in "Assembly Design". I tried right clicking on the part in the tree, then selecting open with but I get the following message "The selected component is already opened as a root in an authoring editor". 

I also tried searching for the part> selected "Open with"> selected "More apps" and tried to select sheet metal design from "my apps" but nothing happened.

How can I open the part so I can continue to work on it in sheet metal design?

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