In July of 2019, I visited Stolac area with the focus on nearby stećci sites, Radimlja and Boljuni. Both are included on the Stolac ensemble tentative submission, in addition to already having been inscribed with the serial stećci property. Radimlja is an accessible and well-maintained necropolis, with some interesting tomb decorations. Boljuni is an out of the way and largely forgotten cemetery.
Aside from the graveyards, I made an all too brief stop at the Inat Ćuprija Bridge which offers a nice perspective along the river, with the nearby mosque of Hadži Alije Hadžisalihović as the main visual highlight. The walls of the Old Town at the top of the hill above the present Stolac looked like a potential point of interest, but exploring them did not fit into my time constraints.
Overall, I did not see enough to suggest that Stolac is a worthy candidate for a future WH inscription, but my short time in town was likely insufficient to form an educated opinion.
Stolac is a bit over half an hour away from Mostar, on the way to Dubrovnik.