Yes, you can delete a duplicate open 'Partial' stocktake. You cannot delete an open full stocktake.
To do this, please follow the below instructions.
From [Dashboard], go to [Inventory] [Stock locations].
Click on the name of the stock location where the duplicate stock take is located.
3. Inside the Stock location, click on [Stock takes] tab.
4. Click on the  box of the line of the open duplicate stock take.
5. In the pop up window, click the red [Delete Stock take] button.