The best place to make Salamander bestiary is Salamander cave in Venore. It's located just outside the city boundary of Venore near the south gate. There is a map mark - link.
The best is last floor, you can also make easy bestiary on:
- Marsh Stalker
- Emerald Damselfly
- Swampling
- Salamander
If you need only Salamanders then follow the map:
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There you can see how some monsters on the respawn :)