Custom Reports

I am in the process of familiarizing myself with reports and custom reports. I have created a number of custom reports which in principle look OK though in my view useless. For example I would like to run a report on Production orders that show the items that have been “issued” to production inclusive of quantity and value. What I realize is that I can only report on a single record and not on multiple linked records in order to do calculations. The production order only holds the quantity but no unit price which I would have to source from the item record. Also the quantity field for the production record is not available to be chosen as a column in the report. I have read the relevant guides but am less the wiser. Can you please advise as to how these reports are to be created?
Is there an interface available I could use to read the Manager database from MS Excel? What database is the Manager data stored on?

Currently, you cannot produce a report with the information you desire. Custom reports do not presently expose all variables. And they are being improved to eventually expose all data.

Also understand that cost of input items on a production order (not price, as you wrote) is a moving target. Production orders transfer costs based on the current average cost of items used, which is not a stored value. It is calculated on the fly when needed. So you will need to get that information from the General Ledger Transactions table, employing a filter for the account name—either Inventory on hand or Inventory - cost, and choosing credits or debits accordingly.