Hi Wyler,
MapTiler distributed via Mac App Store is targeting hobbyists and casual private users rendering a few maps. Rendering multiple input files is not possible.
For professionals and business we have significantly improved MapTiler Cluster product:
http://www.maptiler.com/. This support many MANY more options - including rendering multiple files into a seamless map, setting of zoom levels, full automation and possibility to integrate the tool into a complex workflow, it is much faster on powerful computers, you can control the transformation methods, output formats, detailed settings for size and color optimisation, etc.
We can provide you with a demo so you can try this version on your computer with your own data - just contact us at
in...@klokantech.com.
Regards,
Petr
P.S.
A couple of small maps can be combined into a VRT on a command line, then they would render with MapTiler under Mac too.
You can also use our open-source GDAL2Tiles instead of MapTiler, but then it will take a while for larger files, and you have to prepare your data more properly and do optimisation during post-processing, etc.
By purchasing MapTiler Cluster you save yourself a lot of time and you will get the best results our of the box even for very large input files - we have been automating the whole rendering process maximally during the last years.