The sentence builder itself is rather simple, just drag and drop then read the words into a string. It's actually the processing of sentence that took a lot of work, and honestly I think that would probably make a good topic for the next devblog.
There actually is a History button (the <- arrow in the top left) which is currently used. A back button might also be a thing, but I'm slightly unsure how to get that to mesh well with Yarnspinner at the moment.
As for alphabetical sorting, would you think it's a good idea to be able to switch modes of how the dictionary is sorted (alphabetical, order of appearance, etc)? Right now its sorted based on behind the scenes grammatical reasons that aren't that visible yet.