You can save/download your Track Portfolio, Track Watchlist, and Stock Analysis Pages via CSV file. This will let you keep local copies overtime and do custom analysis with the data.
Track Portfolio & Track Watchlist Page
In the action bar, click the "Download as CSV" button.
This is what it looks like on the Watchlist Page.
It can also be found on the following Portfolio Tracking tabs:
-Portfolio Overview
-Dividend Insights
-Dividend History
-Activity
Here is an example pop up. Click the green "Download as CSV" button. This will save your CSV file.
Stock Analysis
Grey "Download as CSV" button. Found at the bottom of every table.
It is available on the following Stock Analysis tabs:
-Financial Statements
-Key Financials
-Dividends
-Shares Outstanding
-Price Ratios
-Other Ratios
-Stock Splits
-Peers