Pipeline to write to Google Spreadsheet triggered by spreadsheet import

I think that it's somewhere on the Pipelines roadmap to have what is called a bulk trigger. That would allow you to trigger some action after a grid edit or an import, anyways that's my understanding. 

But meanwhile,  as they say, we are where we are, so we don't let the things that we can't do stop us from doing the things we can.

As it happened I was just reviewing an app I did about six months ago and I had the same problem. Here's how I solved it.  

I created a admin record with the Record ID of 1 and linked it to all my detail records.

I created a checkbox flag field on the Parent Admin record to indicate that children had been created but had not yet been imported to the next step of the process, in your case that's the google sheets process. 

A pipeline triggers whenever a child was created and it updates this flag to checked. Now of course that pipeline will have fired say 100 times in quick succession but the checkbox would only get checked once, and the other 99 times the pipeline would I have no effect because it would set the checkbox to be checked when it was already checked.  

I set up a pipeline to watch for the admin checkbox getting flagged and then I use the Clock step in Pipelines to put in a delay of say 15 seconds.   That will give plenty of time for the Child records to all get created in QuickBase. 

Then after those 15 seconds the pipeline moves on to process that batch and the last step in the pipeline is to reset the admin checkbox back to unchecked, and hence waiting for the next child record(s) to get created sometime in the future.