In this paper, we study the effect of a hole-shaped structural defect on the size and density, as well as the thermal stability of skyrmions and the skyrmion lattice in a magnetic monolayer with a triangular lattice and a planar Dzyaloshinskii−Moriya interaction, using the local relaxation method and Monte Carlo simulations. Achieving control over the skyrmion density opens possibilities for the design of functional skyrmion-based devices. It is shown that increasing the Dzyaloshinskii−Moriya parameter increases the skyrmion density, while the presence of an external magnetic field promotes the degeneracy of the mixed configuration of skyrmion-domains into the skyrmion lattice. We demonstrate that the presence of a hole-shaped defect does not affect the phase diagram of the skyrmion gas and the skyrmion lattice, but acts as a stabilizing factor against thermal fluctuations. The thermal stability was studies using Monte Carlo simulations to calculate the order parameter and the order parameter susceptibility. It is shown that for certain combinations of the external magnetic field and the Dzyaloshinskii−Moriya parameter, there is an optimal size of the structural defect that allows achieving the maximum critical temperature of the phase transition The results obtained in this study can be useful for assessing the size of the defect and the values of interaction parameters in a magnetic material with high transition temperatures in the presence of a strong planar Dzyaloshinskii−Moriya interaction.