Headword and gloss are in the present indicative, third person plural. For the headword verb, ἐγκαθίζω see generally LSJ s.v., illustrating its military and other senses.
[1] Despite Adler's marginal indication ('Thdr. + E'), there is no clear connection with Theodoret. Rather, what is being glossed here could be Philochorus FGrH 328 F108 (the only extant instance of ἐγκαθίζουσιν as opposed to ἐγκαθίζουσι ), from the scholia to Euripides, Hippolytus 35: the Pallantidai do this at Gargettos (but Theseus eludes them).
[2] Dionysius of Halicarnassus, Roman Antiquities 9.20.2 (probably via a lost part of the Excerpta Constantini Porphyrogeniti). Cf. epsilon 2358.