Recently, the Pastorals seem to be having an outsized presence in Mohr Siebeck’s Wissenschaftliche Untersuchungen zum Neuen Testament series. The following are recently published and forthcoming volumes in WUNT 1 and and WUNT 2 which each focus solely on one or more of the Pastorals. Authorship/editorship is widespread: Australia (Kidson), Germany (Herzer, Zimmermann), Nigeria (Manomi), Switzerland (Bulundwe), USA (Langford).

Lyn Kidson, Persuading Shipwrecked Men: Rhetorical Strategies in 1 Timothy (WUNT 2/526; 2020) (RBL review) (JETS) (ABR) (JSNT)
Dogara Ishaya Manomi, Virtue Ethics in the Letter to Titus: An Interdisciplinary Study (WUNT 2/560; 2021)
Jens Herzer, Die Pastoralbriefe und das Vermächtnis des Paulus: Studien zu den Briefen an Timotheus und Titus (WUNT 476; 2022)
Ruben Zimmermann and Dogara Ishaya Manomi, eds. “Ready for Every Good Work” (Titus 3:1): Implicit Ethics in the Letter to Titus (WUNT 484; 2022)
Andrew M. Langford, Diagnosing Deviance: Pathology and Polemic in the Pastoral Epistles (WUNT 2/ ; 2022 est.)
Kampotela Luc Bulundwe, 2 Timothée dans le corpus paulinien. Analyse mémorielle (WUNT 2/ ; 2022 or 2023)

To be sure, plenty of single essays on one or more of the Pastorals have appeared in edited WUNT collections. However, before the recent spate of volumes just noted, only the following WUNT volumes (to my knowledge) focused solely on one or more of the Pastorals (or, for Trebilco and Smith, were monographs with a very significant Pastorals component):

Ulrike Wagener, Die Ordnung des “Hauses Gottes.” Der Ort von Frauen in der Ekklesiologie und Ethik des Pastoralbriefe (WUNT 2/65; 1994)
Andrew Y. Lau, Manifest in Flesh: The Epiphany Christology of the Pastoral Epistles (WUNT 2/86; 1996)
Hanna Stettler, Die Christologie der Pastoralbriefe (WUNT 2/105; 1998)
Paul R. Trebilco, The Early Christians in Ephesus from Paul to Ignatius (WUNT 166; 2004)
Bernhard Mutschler, Glaube in den Pastoralbriefen: Pistis als Mitte christlicher Existenz (WUNT 256; 2010)
Claire Smith, Pauline Communities as “Scholastic Communities”: A Study of the Vocabulary of “Teaching” in 1 Corinthians, 1 and 2 Timothy and Titus (WUNT 2/335; 2012)

The first batch of volumes above has six WUNT volumes on the Pastorals being published in around four years (2020–2023). The earlier batch of volumes, another half-dozen, spans nearly two decades (1994–2012).