Please check this thread where this has previously been asked: https://community.qlikview.com/thread/178574
There is no official functionality available for write back at the moment from Qlik Sense. There are also no extensions available to do this. As Qlik Sense is a tool for visualizing the data instead of capturing it, it is unlikely that they will provide this functionality in the future.
Hope this helps and if you are satisfied with this answer then please mark it as correct, thanks.
Pomerol Partners has developed a Qlik Sense writeback extension...
Here is a quick video http://pomerolpartners.com/US/Data-Entry-Extension
Feel free to contact me