Can I use the snipping tool to take a screenshot of the windows 8 start screen or modern apps?

One of the tools I've found invaluable in answering questions on SU is the snipping tool. I may on occasion need to take screenshots of part of the start screen or 'modern' apps. I may not want to take a complete screenshot, and while I can use PrtSc and switch back into desktop to paste it, this is clunky if I need to document a multi-step process.

Can I use the snipping tool on modern apps or the start screen? If not is there a configurable way to save a series of screenshots to a fixed folder, say when I press a combination of keys, so I can work, screenshot, then crop and annotate the folder of images?

Answering the last part of your question, as per this question pressing Windows + PrtSc will save screenshots to your Pictures folder.

No, you cannot. I have even tried putting Windows 8 UI apps on a second extended monitor, but the tool just can't see the apps.