So far (we don't have documentation yet!) we have two main resources:

A recorded presentation from Odoo Experience

The commit where we describe the feature a little

Purpose -  In several businesses, it might be cumbersome to properly calculate a quote (define an appropriate quantity, price, etc). The goal of this task is to allow user to easily access a spreadsheet (blank or preconfigured) to do those calculations.

Specification - From a quotation template, you can create a spreadsheet calculator template. At creation, a list of sale order lines is inserted with a global filter allowing to filter the lines according to their quotation. 

You can add "Field sync" rules on any cell (right click on a cell) to update one field of one order line in the list (readonly fields are excluded). 

Then, when you create a quotation from the quotation template, you can open the spreadsheet calculator. It creates a copy of the spreadsheet (allowing you to play around values etc.) and adds a global filter to filter the sale order lines from the quotation. 

From this spreadsheet, by clicking on "Save in SO00XX", it reads the values in cells with a "Field sync" rules and updates the quotation lines with those values. 

This allows to create very specific flows with any arbitrary computations to compute any values in sale order lines, based on any data, from the spreadsheet itself or from the database by inserting other data sources in the spreadsheet template, for example, employee planning, products, stock, etc.

This great power and flexibility comes with limitation about how generic it can be. It's expected to hardcode product names or ids in formulas in order to match order lines. Hardcoded names are of course not robust to different languages, ids are robust to that but are less friendly and are not cross-db compatible. Each spreadsheet calculator template must be built specifically for every use case and every database.