Since Minecraft uses textured blocks and Qubicle only supports single colored voxels you have to use a workaround to create Minecraft models. Qubicle supports up to 256 block colors that are translated into Minecraft blocks during import and export. Use Games > Minecraft > Edit Blocks to set colors for BlockID/DataID pairs.
Minecraft Schematic Export
For every voxel that you want to export Qubicle looks for a matching block. The color of the voxel must precisely match the color of the block. If no block is found then the voxel will be ignored. So to make this work all voxels' colors must match a block color. Use Games > Minecraft > Apply blocks to ensure that this is the case.
Minecraft Schematic Import
For every imported voxel Qubicle looks for a block with the matching BlockID/DataID pair and colors it accordingly. If no matching block is found then the voxel's color will be set to Fuchsia #FF00FF to make it easily identifiable.
Opens the Minecraft Block Editor which enables you to modify the blocks that are used for Minecraft Schematic import and export. Here you can change BlockID/DataID as well as the color and the name of the block. Furthermore you can disable blocks that you don't want to use for the Apply Blocks and Create Swatches actions. To quickly enable/disable a block double click its list entry.
Resets all blocks to default.
This actions recolors voxels so that they perfectly match block colors. Only enabled blocks are used. For each voxel Qubicle looks for the block which color resembles the voxel's color the most. Use this action before exporting to Minecraft.
Creates a swatch for every enabled block and adds it to the swatch map.