Terrain set for narrow area

This is the screenshot to demonstrate what I want to achieve. Notice the area that I annotated with a box.

This is my tileset file (free assets from Kings and Pigs by Pixel Frog)
Terrain (32x32)

I tried many different ways to set up the terrain, but most of the time, the terrain brush has the size of 2tilex2tile. With some setup, the terrain brush can be 1tilex2tile or 2tilex1tile but the result is very messy.

I ended up using the 2tilex2tile terrain brush for most of the part and modify by Stamp brush. That’s how I got the result above.

I’m not very experienced with the tool and don’t know whether I’m missing something obvious. Or the tool just does not support that for this tileset format.
Please someone enlighten me!

Have you tried setting up a Mixed terrain set? This looks designed for that, and Mixed terrain sets can handle these 1-tile-wide scenarios.

Thank you for your help.
I don’t have much experience with the terrain feature.
I used the same tileset with bitmask and it worked okay.
Just wonder if the tileset is suitable to use with tiled’s terrain.

Is there any example for using mixed terrain?

Terrains are very similar to bitmasks, so if you got it to work that way, it’ll work as a Terrain. The labelling should even be very similar.

This set is basically two “blobs”, 47-tile subsets of mixed terrains, Tiled supports these.

If you want to always paint within the purple void rather than on an empty layer like my example, then label all the unlabelled corners and edges with the “Wall” terrain, and make sure your map is filled with either the base floor tile or the purple wall interior tile before you start drawing.
The 1x1 blocks (wall with wall edges on all sides, floor with shadows on all sides) have their probability set to 0, Tiled isn’t great at using these tiles (yet!) so they have to be placed manually, not via Terrains. But they should have labels so that the Terrain tool knows how to connect other tiles to them.

I did run into some small issues while using this set of labels, but I think that’s due to bugs in how Tiled chooses which tiles to paint, rather than any incompatibility between Tiled and this tileset. Hopefully that’ll get fixed, I posted about it in the Tiled Discord.

Wow, thank you so much for the help.
Now I quite get the big picture on how things work with the terrain feature.