Yes, a habilitation at the Faculty of Arts and Humanities is generally possible. However, according to § 6 Section 1 Nr. 5 of the Habilitation Regulations of the Faculty of Arts and Humanities of the University of Cologne (27.06.2016), the habilitation procedure for junior professors with tenure track must be completed before the tenure-track procedure (final evaluation and acceptance).
After successful acceptance of a position, a habilitation is no longer possible. In accordance with § 6 (4) of the Habilitation Regulations, a habilitation procedure already initiated will also be terminated when a junior professor with tenure track is accepted into permanent employment after a successful final evaluation.