Drag and drop to move pages in a tree
- No dead space. Have as much drop zone as possible in between rows. Do not waste them as gaps because it would be frustrating to drop a page where it seems reasonable and nothing happens.
- Show the outcome, or show nothing. Have an indication, such as line, to indicate where the drop will be (i.e. indented according to the level). When a drop is not possible, show no indicator.
- One indicator per outcome. There should only be one indication for one outcome. For example, there is only one outcome between two same-level pages but there could be two indications, one below the page at the top and one above the page at the bottom. A solution is to have only one drop zone, such as "before this page" but no "after this page". But note that two nearby positions could be for different results, such as drop as child or sibling, and they should have two indicators.