Document master/slave/terminal linking, the feature nothing in the collection uses The element editor can declare a master's contact budget, cap how many slaves may attach, mark a terminal as isolating a potential, and keep an element out of the BOM. None of it was documented anywhere, and the measured result is that none of it is used: of the 6918 elements in the 10_electric collection, 0 declare slaveContactGroups and 0 declare max_slaves; no shipped example project uses auxiliary1-4. Adds element_linking (EN/FR/DE) as a guide, and turns the one-line kindInformations and elementInformations reference stubs into the actual XML vocabulary, taken from ElementData::kindInfoToXml/kindInfoFromXml. Records two traps worth knowing: max_slaves counts slave elements rather than contacts, and potential_isolating / auto_num_locked / exclude_from_bom are compared against the exact string "true".