Custom Workflow Actions in SharePoint 2016

SDK2013 is still valid for 2016 - https://help.nintex.com/en-US/nintex2016/current/#sp2016/SDK.htm 

Thanks for the reply!

Yes, I saw that, but I'm really confused that when you're creating a Visual Studio from Nintex template the code uses so many obsolete and deprecated methods and classes...

So, it's my huge concern if it worth it to use deprecated methods.

yeah, I understand that.

you may try to open a ticket with ‌ if they have any up to date info what are plans with SDK.