formal synonym of "trotzdem" — "nevertheless". Slightly more written-register. Position 1 + inversion.
Konjunktionaladverb konzessiv — formell; Position 1, Inversion.
Порядок слов
Hauptsatz 1
Subj.
V = 2.
…
,
Sie
hat
wenig Zeit
,
Hauptsatz 2 mit dennoch
Konj.-Adv.
V = 2.
Subj.
…
dennoch
hilft
sie
uns.
A Konjunktionaladverb takes POSITION 1 of the second clause, so the verb lands in 2nd and the subject is pushed after the verb (inversion). This is the key difference from coordinating conjunctions (und, aber, denn), which stand outside position 1.