In SUD, the mod relation is used for all modifiers (as opposed to UD set of label amod, advmod…).
Hint
Most of the times, mod is used without extension or deep feature.
Possible extension or deep features:
Other deep features appear during conversion from UD => SUD, UD subrelation are kept as “deep” SUD relation for information preserving.
For instance, UD:nmod:tmod => SUD:mod@tmod.