I went off on pretty much a tear earlier investigating the possibility of coming up with some kind of rapid communication board which would allow you to input words, not letters.
I went once or twice around the bend, and found the closest match in an app called DocsPlus which gives you the ability to create customizable word-bars. There’s a 28 day free trial. It’s interesting, but my use case is to be able to rapidly paste in the results of these sentence creation actions into Firefox in a spreadsheet. It was too combersome with switching back and forth between tabs to access other word bars.