The use of the "object dot" syntax is experimental. I suspect that the only folks who might be able to find out an answer to this are the ones in Tech Support. I do know that with regular data step and ODS (current) syntax, there is a way to CHANGE the object label.
On the FILE PRINT ODS statement, you use the OBJECTLABEL option: http://support.sas.com/kb/23/425.html
I'm guessing that, in your syntax, there is some default for LABEL: when you declare the object -- even if you don't give one explicitly, then probably the NAME: is used. There's got to be something to indicate the object in the SAS Results Window. However, short of looking in the information on the topic http://support.sas.com/rnd/base/datastep/dsobject/#new
or contacting Tech Support, I don't know many folks who are using this yet. I don't know whether the usual SAS tricks will work here:
label: '00'x or label: ' ' -- there's a distinct chance that if you blank out the label the name will be used anyway.
At this point there a way to manipulate the bookmarks. However I think your suggestion is a very good one. I will enter a defect to suggest adding an option to the table_start method. A new bookmark will be created every time you do a table_start().