Not for direct text-field dictation.
Apple does not give Action Button shortcuts the same active text-field access that a keyboard has. That means the Action Button cannot work as a hold-to-record, release-to-paste trigger into whatever field you are typing in.
For text-field dictation on iPhone, use the Monologue keyboard and tap the Monologue microphone.
If you want to change the formatting style before dictating, open the Modes menu in the Monologue keyboard and choose the mode you want, such as Email.