A great help to me while debugging would be the ability to collapse code based on a range of lines. Oftentimes I'll need to look at two separate areas of the same file and right now have to scroll quite a bit.
The way I see it working is highlighting a series of lines and clicking a collpase button. This would collapse those lines into a single line with a place holder in the line number gutter. Clicking the placeholder would expand to code back to normal. This should be easier for you to implement than a tag based collapse.