I think that's not possible.
There was the same question some time ago and if I remember it correctly,nobody found a solution.
You have to hope that this feature will come with an future update.

Further research has shown that on the second monitor one cannot right click. Basically, the right click does not show anything as far as the menu, it feels like the second monitor is just there to display and (extension ) of the picture but not of the desktop. Just so everyone knows I am able to gain functionality using other distributions like Ubuntu and mint, including Manjaro.

My wish is to bring more people to test Deepin, since for me it works great with my hardware.