I have bought a tileset with cliffs and, being a bit of a noob, don’t really know how (or even if it is possible) to use the terrain tool on these cliffs to let the terrain tool allow quicker generation of seamless cliffs/mountains. Can someone give me a pointer?
The terrain tool is specifically for flat terrain tiles, so with transitions between terrains within each tile. It can’t deal with the much more complex set of tiles that are needed to transition between these different heights.
Tiled has a more complex but also more versatile system called Automapping, which you may be able to configure to automate the placement of those cliffs. It requires setting up maps with pattern matching rules. Similar cliffs to yours have been automated with automapping in the Source of Tales project, so you could check out the rules used there (see the folder named automapping).