In this paper, we investigate the algebra of upper triangular matrices \( UT_n(F) \) , endowed with a \(\mathbb {Z}_2\) -grading (i.e., a superalgebra) and equipped with a superinvolution. These structures naturally arise in the context of Lie and Jordan superalgebras and play a central role in the theory of polynomial identities with involution, as shown in the framework of Aljadeff et al. (Proc Am Math Soc 145(5):1843–1857, 2017). We provide a complete description of the identities of \( UT_4(F) \) , where the grading is induced by the sequence \((0,1,0,1)\) and the superinvolution is the super-symplectic one. This work extends previous classifications obtained for the cases \( n = 2 \) and \( n = 3 \) , and contributes to the study of an open problem for \( n \ge 4 \) . In the final part of the paper, we investigate the image of multilinear polynomials on the superalgebra \( UT_n(F) \) with superinvolution, showing that the image is a vector space if and only if \( n \le 3 \) , thereby contributing to an analogue of the L’vov–Kaplansky conjecture in this context.