I was just about to write a freature request when I saw this post.
One of the few things that I really liked about Eclipse as an IDE for Salesforce was their option to right click within the code screen to pull up a menu where you could click to Deploy that single file to the server.
It looks like the attached image.
The way I think this translates to Welkin is you have a deploy to server button and when you click on it then you get the deploy screen with only the box checked off related to the file you right clicked on with all the other boxes left unchecked.
Now granted compared to Eclipse there is a bit of an issue. You could be deploying a version of the file that is not the most recent if it has not been built yet but that is ok, I think its on the developer to make sure they have built the file.
For lazier developers such as myself this was a real time saving feature with Eclipse especially when your workflow includes worst practices like deploying and testing on production instead of in the Sandbox. Having this feature makes this sort of iteration a lot more convienient.