My advice was to narrow your question down as it is overboard.
"How to configure a button to run script is a separate consideration - ask about it in a new question."
QuickBase does not provide a simple way to attach script to a button on the application dashboard. The buttons it does allow you to place on the dashboard do not run script but rather load the page specified by the URL. The easiest way to get a button on the application dashboard to run script is to place the button in a minimal report and place the report on the dashboard. The button can then be a formula URL using the JavaScript protocol or some type of formula rich text field which when clicked on will run the relevant script.
Another simple approach is to create a simple HTML code page with the button and place the code page on the dashboard through a web page widget. This second approach requires you to write some simple type of HTML page with script mindful of the fact that the script will execute in the context of the containing <iframe> associated with the web page widget.
Other techniques to add a button to the application dashboard would entail using BOL, SW or some other script injection technique to alter the application dashboard's native behavior.
In many cases it isn't worth the effort of placing the button on the application dashboard itself but rather just create a new table called Tasks and include button in this table. Then place a report with all your Task buttons on the Tasks table homepage.
Your further questions about using async/await or concatenating child records should be in their own thread.
