If you're using IC61, you could create an incremental technology database, and then just define those layers in your own techfile, which then references the standard technology library you're using.
But apart from that, I don't believe OpenAccess has a means of creating a group of layers (I may be wrong). Of course, you can add some additional layers and not mark them as "valid" so they won't then appear in the LSW, but your SKILL code can create and use them like any other layer. You won't however be able to graphically select them in the layout if they're not valid - but you could just change that on the fly...
Best to read the documention on the technology file, so you can figure out what is the best fit for whatever you're actually trying to do.