I would like to perform a few regular maintenace jobs with my HP Deskjet 6940; however, without a current manual (O/S is Windows 7 32-bit) I have no idea what the "toolbox" is that is referred to when trying to accomplish these simple tasks such as cleaning the printheads.

Hi,
Although this is an old printer, there are still ways on how you can do maintenance on the printer.
Try to open a program that you are trying to do printing like word. click on file then choose print choose properties, instead of print (the properties might varies to option, preferences or set up) Choose features of the printer then the printer services. this will try to pull up HP toolbox.
Also if the printer had a control panel, you can use that panel to do maintenance as well.
Here is one of the use full link for you to check on how to use the control panel on the printer.
http://h10032.www1.hp.com/ctg/Manual/c00591688.pdf
I hope this will actually help you resolve your issue.
Thank you for choosing Fixya

1. Turn on your computer, wait for it to boot up, then turn on your printer and load with paper.
2. Locate the " HP Imaging Director " icon on your computer, it would have been added to your
monitor screen when the printer was installed.
3. Double click this icon and a screen will appear showing the functions available on your
printer.
4. Click on the " Settings " heading, scroll down to "print settings" and over to "printer toolbox".
5. Click on "printer toolbox" and you will be taken to the maintenance window.
6. From this window, choose what you want to do.