It's been a long time since I've done weldments, do the sketch elements have symbolic representation ie.. line1@sketch15inpart.prt ?

Configurations on the other hand, it sounds like your configuration concept is incorrect.

Parts have configurations, assy's call up these different configurations.

1st deal with configurations in parts. You can suppress/resolve/modify features with configurations in a part. Even sketch relationships are controlled by configurations, which I've never done in real life. To do this, you have to create the configuration first. Then when making a change to the part, tell SW this config only, hopefully your new confguration, the default is to update all config. Making a change to a part does not create a configuration.

2nd in an assy. You can suppress/resolve/refer to different components in an assy. You can not change a part's configuration in an assy, you can only pick which part's configuration you wish to use.

Another issue with configurations. Let's say we have a top assy, sub assy then a part in the sub assy. There is no way to control the part configuration through the top assy. The top assy can access the sub assy configurations, and the sub assy can control the part configurations. The top assy has to go through all the different assy levels.

In a top assy, editing a part in the assembly, you can't produce part configurations. ...ok, you can deal with top down configs in the later releases, but if you haven't built the configurations from the part level upto the top assy level. I don't think you'll ever be able to master building from top assy level down to the part level.