When attaching a file to a Manager transaction, a copy is made and stored internally in Manager. The original can be moved or deleted.
I agree searching or sorting by attachment status (as well as date and other features) within Manager’s summary page drill down would be a useful enhancement.
The original can be saved in any location on your computer. Having folders by year is reasonable if you’re keeping them also. However that functionality is appropriately completely outside Manager and typically provided by your operating system.