I don't think so (but I think you're right about what the problem is). default_context is a System Setting, so you'd have to create a User Setting with that key and the correct value for each user. That should work, but I've never tried it.
You could write a simple utility snippet that created all the User Settings, or a plugin that set it automatically at some point.
If that doesn't work, you'll may have to teach users to right-click on their Context.
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PLEASE, PLEASE specify the version of MODX you are using.
MODX info for everyone:
http://bobsguides.com/modx.html
[ed. note: BobRay last edited this post 14 years ago.]