Hi Dan,
Somewhat oversimplified, here's how I understand it...
Tagged values are not quite like other attributes. They originally were an extension mechanism, allowing UML to transcend its design boundaries. That is, you could use tagged values to represent additional properties - whether attributes or other subtleties did not matter, just so long as the 'extended' property could be identified with a name and have its value expressed as a string - beyond those that UML provided by default.
This is still a major function of tagged values of course. As UML has come to be used for more things, whether through custom extension via profiles or through specialized dialects, tagged values have become invaluable. For example, EA uses tagged values to easily capture things - including some that are part of the standard UML - that are not well handled by the core schema. While this is not quite what UML (originally) had in mind for tagged values, it is a perfectly reasonable way to use them.
Back to your situation. It seems that tagged values would work best for you if they could be treated like any other attribute. Ideally this is how they should work, at least in a profile. My guess is that you've run into the EAUI here. You could make a feature request to Sparx regarding some way to turn this off. Perhaps it could be added to the Tools | Options | Objects dialog as a global option. It might operate something like the options to group attributes by stereotype, or sort them alphabetically.
I'll leave you to decide whether to make the request. If you do, I strongly suggest you either start a new thread in the S&R forum section and cross reference the new thread and this one, or simply post back here to tell us what you suggested.
David