having the ability to type the expression inside of your spreadsheet with some sort of trigger that lets app sheet know that the text string that follows is to be used as an app formula to be applied to the column. it would greatly reduce the time it takes to do this in app.
for example if you wanted to some by date you would have to write the formula SELECT( Orders[Total Amount], AND( ([Customer] = [_THISROW].[Customer]), ([Order Date] >= [_THISROW].[Order Date]) ) ) ) individually in every column you wish it to apply to. now if you only have a couple columns it's not that bad, but if you have 15,25,50+ columns it is very tedious to do. Where if there was an ability to place the expression inside of the spreadsheet, the task could take less than 60 seconds.