Fusion916 Yes that is possible in fact it was one of the reasons I joined the project.
In pcb-rnd we have very good layer system at this point. It's one of the largest advancements we made over the mainline of pcb. It took a lot of work but at this point you can both add and subtract from the solder mask layer. There are several ways to do it.
1. The simple way: Turn visibilty on for the solder mask layers and use the polygon, line, arc, or text tools to draw and the features they create will be subtracted from the solder mask.
2. The subcircuit way: This is for people who want to have things like footprints that use pads as heatsinks (where you want exposed copper but solder paste is optional) or for people who are doing microwave design like hairpin filters.
http://repo.hu/cgi-bin/pool.cgi?cmd=show&node=subc1On a related note we now have a more functional thermal tool.
http://repo.hu/cgi-bin/pool.cgi?cmd=show&node=thermalsIn the mainline (2014 release of pcb) it was done by making elements that fit over the traces but this was painful, time consuming and very unpleasant to edit.