You can drag any template into any other template. A template can be blank - New Template - voila - blank template. A template can be one or any number of components.
A template can be draged in by its name, or by its preview and when done from the preview, you can even select the drag in point.
So, when dragging one template into another, while still holding down the left mouse button, press the right mouse button to open the right click menu. Once the menu is open, you can actually let go with both buttons and the template will still be anchored to your mouse.
Next, select Reflect off of the menu. the template will now be flipped. Drop it anywhere and then select the original origin point and right click to open the menu that will let you reset the origin to this point.
So now you are probably asking - what is Mirror as opposed to Reflect? If you are dragging in a half template and want it symmetrical, Mirror lets you bring in both sides at the same time.
Sometimes I make a Scratch folder and place partial or scratch copies of templates in there and remove the unwanted components to then drag the remainder back into another template.