Check out Bruce Foster's ImpGraph plug-in: http://home.comcast.net/~bruce.foster/ImpGraph.htm
Otherwise, no you can't (re)set defaults. However, some settings in FM are "sticky" and will be retained for the next operation.
Here it is two years later and I decided to look for an answer to the same question. I tried the above link but it's broken. Do you or any other forum member know if Bruce Foster moved the web link to another location? Or is there another plug-in available?
I use anchored frames below current line, a fixed with, centered, with graphic objects centered left-right (don't know if that last one is part of the anchored frame).
As Jeff mentions, Bruce passed away and his plug-ins are no longer available. There is a fairly extensive list of plug-ins compiled by Lin Sims and can be found at either http://mif2go.com/framemaker-resources or http://www.microtype.com/links.html
You might want to have a look at Russ Ward's WS utlities plug-in at http://www.weststreetconsulting.com/WSC_Utils.htm or Felix Ritter's fmGraphicstools at http://www.mevis-research.de/~ritter/awakeideas/fmtools.html