I haven't looked through the React code yet, but just a quick tiny thing I'd do is add padding-bottom: 1rem, padding-left: 1rem to the .control_button-as-heading class. The dropdowns look a bit weird on my browser with the arrow ending up under the text, whenever I added those two lines of CSS (overriding the padding already set) to that class they line up with your textbox and look much better (at least on my screen). Just thought I'd share that in case it's not just my browser that the dropdowns look a bit funny on.
The functionality looks great and works exactly as I'd expect so good job on the main program! I like the loading screen (i assume) Suspense component use. I haven't looked through the source but it functions great and looks nice so good job!
@steventoben Thank you a lot!