Just like in real life, SH3D and even you can't bend a straight object (chair, table or box) without breaking it.
Also, just like in real life, if you need it, you can create it (and SH3D can do that).
You could do this with the help of room or wall.
1. From room:
1.1. Add a level and set the floor thickness at the height of needed object.

1.2. Draw bounding walls and curve the necessary.



1.2.1. Fill the space with a room OR
1.2.2. Use Autodimensioning plugin to generate the build surface.

1.3. Select the generated room and 3D view -> Export to OBJ format.



2. From wall:
2.1. Draw a wall, set the height, the thickness and the curve.
2.2. Select the wall and export it as object.

3. Furniture -> Import furniture... and import the exported object.


For more precise and funny you could use Multiplier plugin.