Try running the Verify image libraries command http://wiki.ubotstud...image_libraries in ubot studio, run that, and wait a couple minutes for the required library to install in ubot's roaming libraries folder. You can verify that it has installed by visiting %appdata%/Ubot Studio/Libraries/ in file explorer. The library that is installed is called imagemagick https://www.imagemagick.org, and so you will see a zip folder and extracted folder of the same name when it is installed.
When that is done try running your combine images command.
If it doesn't work, go to the extracted imagemagick folder and try opening any one of the .exe's in it. If windows shows an error "This App Can't Run on Your PC" then the imagemagick library is not compatible with your machine. I see this error when using these commands on a 32 bit windows machine.
When used on a 64 bit windows machine the combine images command does indeed work in latest version of Ubot - 6.1+.
Thanks - I just get an error "The given key was not present in the dictionary" when running the verify image libraries command