All things are poison, and nothing is without poison; the dosage alone makes it so a thing is not a poison."
Like with so many things in life, it’s a question of willingness to take a risk and of personal health and individual metabolism.
The general rule is that raw elderberries shouldn’t be consumed because they contain cyanogenic glycosides, i.e. substances that can be transformed into cyanide and ultimately cause cyanide poisoning. As with all plant-based substances, the content can and will vary a lot depending both on the specific strain of plant and the environmental conditions, including soil composition, water or rain and change significantly during the life cycle and ripening stages. For elderberries, the content of cyanogenic glycosides decreases significantly in fully ripe berries, some researcher1 found as little as 0.0054 mg hydrogen cyanide equivalent per gram of berries, which is roughly 0.0001 mg per berry. Considering that a healthy adult human can safety ingest 0.02 mg per kg of body weight, a few ripe berries should be harmless enough. This is the same reason why eating a few apple pips (containing amygdalin, also a cyanogenic glycoside) is harmless.
The numbers above should also explain why individual reports of toxic effects vary so widely, from no effects at all to severe digestive issues.
If you want to consume unheated elderberries, I recommend you chose fully ripe berries and limit the intake to just a few initially (see the numbers above and go way below the statistically safe threshold because individual tolerances may be lower). Note that this post is not an endorsement, it’s just to help you make an informed decision.
The drying process is the same as for other berries - ensure good ventilation and place them on a cloth or fine netting, because the berries are so small. If you want to use a dehydrator, you may have to cover the trays with cloth or mesh if the slats are too wide. Consult the manual for settings.
Petra Demmer: Kapillarelektrophoretische Untersuchungen an cyanogenen Glykosiden. Inaugural-Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften im Fachbereich Chemie und Pharmazie der Mathematisch-Naturwissenschaftlichen Fakultät der Westfälischen Wilhelms-Universität Münster. Münster 2004, urn:nbn:de:hbz:6-28659388497.