How can I 'save' a cell order in columns in Google sheets, sort the column to a different order, then reload the earlier cell order?

I'm building a quote for a client, based on their list of tasks.

I've entered these tasks in his order down along my first column (a).

My first row (1) is a collection of headings, which I've frozen.

Subsequent columns contain my notes, my time estimates, cost estimate, etc.

I would like to be able to sort the rows according to numbers in different columns, but then to be able to return to the original order of tasks as specified by my client.

Advice would be much appreciated.