Cobbled together a bit of a solution for anyone who may be interested.
Save the set of chart sheets or Windows Layout as a layout using - Right click > Template > Save > choose file type to save as Chart Template.Complete (*.chart).
Upload the file to http://www.convertcsv.com/xml-to-csv.htm
Leave Output Options in Step 2 set to default (comma field separator, Include header in first row)
Choose ‘XML to Excel’ in Step 3 and save the file to your PC.
Open the file with Excel. It will probably generate an error message, but proceed anyway.
Column A contains the chart sheet names from the tabs.
Hide or delete all columns except those headed Pane/0/FilePath, Pane/1/FilePath Pane/2/FilePath etc up to the maximum number of panes in your set of chart sheets.
Now you have a list of all formula and paths used in each tab.
There’s much more info including the formula themselves if you wish to use it.
(Note: I tried five other online XML converters - two gave semi usable results, one gave unusable result and other two wouldn’t recognise the file.)