The source of a linkA link source is the source of the link where the value come from.
It can come from any parameter create with a right clic-> create link from.
Or it can be an exposed parameter. Go check Expose Parameters as percentage and Expose Parameters as parameters to check that part.
PARAMETERS ON ALL LINK SOURCES
- Modifiers (List of Link Modifiers): Modifiers of the link source
Audio Spectrum - Source of a link that uses audio extraction on an audio channel
Parameter - Source of a link form an element's parameter
Single Precision - Source of a link from a single precision device
Double Precision - Source of a link from a double precision device
Clock - Source of a link from a clock (current time, timecode, MIDI, ...)