If I cast a multiple-target spell with the (D) quality on my friends, can I dismiss the effect from one target while keeping it active on all the others?
For example: I cast hide from undead on myself and all my friends, then decide I want to have a chat with a vampire without exposing my friends. Can I dismiss the spell from myself but still have my friends be affected? Does the answer change if I want to dismiss it from my friend the bard while keeping myself affected?
Dismissability is a duration note on the whole spell, not on parts of the spell. Dismissing a spell has the same effect as the spell's duration ending — because that's exactly what it is, but triggered voluntarily.
To be able to selectively terminate the effects of a spell affecting multiple targets would require the spell itself to offer that ability in its description.
When you dismiss a spell, you dismiss the whole spell. Not just parts of it. Theoretically speaking, the target of your "dismissal" is the spell, not the effect of the spell on a target.
