I was almost ready to prepare elderberry jam, using the elderberry with its seed, but then I found some information about seed's toxicity.
Do you know if the seed of ripe elderberries are toxic when preparing a jam?
From your own link
Although the ripe, cooked berries (pulp and skin) of most species of Sambucus are edible, uncooked berries and other parts of plants from this genus are poisonous. The leaves, twigs, branches, seeds, and roots of Sambucus plants can contain a cyanidin glycoside. Ingesting a sufficient quantity of cyanidin glycosides may produce illnesses.
Cooking destroys the small amount of cyanogenic glycosides found in the fruit that is poisonous.
When making jam you can sieve out all the seeds.