Quickly save Screenshot in MacOS Mojave with keyboard Shortcut
Didn't realise that keyboard shortcut was asked. Jump right to the last para.

You can look at the screenshot in the bottom right corner of the screen. If you think that the SS was taken fine, you can swipe right on it with two fingers(like in Safari) and it will be saved at that moment. 

You can edit it(or maybe not) by clicking on it and then done and share etc will be there. 

You can also drag and drop it if supported by places you want to use the SS at so immediately. 

The question you linked didn't mention "remember selection" in options of cmd+shift+5. So if you uncheck it and the said shortcut, instant saving!