What counts as a neighbour
Stand on a mode, choose one of its degrees other than the root, and raise or lower it a semitone. If the result still has seven notes in the same order and is a mode of one of the seven families, the two modes are neighbours, and the row says which degree changed and in which direction. The root never changes: a mode keeps its starting note, so a neighbour is always read from the same place.
Reading the panel
The panel above opens on Ionian. Choose another mode and it lists every degree that can be altered into a declared mode, links each result to its row on its family page, and says where the mode lands when it is reflected around its root. The choice stays on this page: nothing is added to the address, stored, or sent.
Reading the full list
Below the panel is every pair once, grouped by the pair of families it joins and written in the raising direction: the lower mode, the degree raised, and the mode it becomes. Read a row backwards and it is the same pair with that degree lowered. Pairs inside a single family occur only among the diatonic modes, where a chain of single alterations runs from Lydian down to Locrian.
Why some modes have so few
A mode has at most twelve single alterations — six degrees, each up or down — and many of them run into the next note or leave the atlas. The pairs listed here are the ones that stay inside the seven declared families, which is why one mode may have half a dozen neighbours and another only two.