Arbitrary order xparse e type arguments (embellishments)?

Question

Can I use xparse e-type arguments to redefine how subscripts and superscripts work for a command (e.g., make mybeta put all sub/super scripts in parens)?  I tried defining
 NewDocumentCommand{mybeta}{e_e^}{beta_{(#1)}^{(#2)}}

And it seems to work fine if I place them in the order the arguments are specified but not when I try
 mybeta^{n}_{s}

where I get a double subscript warning when I want $beta^{(n)}_{(s)}$
I'm guessing that maybe I need to use e{_^} as the argument specification but if I do that how do I tell the _ and ^ arguments apart or recover them?  Or is there a different/better way I should be going about this and I've misunderstood the embellishments entirely?

LaTeXereXeTaL · Accepted Answer

The solution is, as you predicted, to use e{_^} in your argument specification. The order of the embellishments doesn’t matter. And yes, it’s amazing that it works!

Peter Gerdes · Answer

Apparently (thanks to @LateXeraXeTal)  you just use
 NewDocumentCommand{mybeta}{e{_^}}{beta_{(#1)}^{(#2)}}

I admit I'm a bit confused as to why you don't use multiple e argument type specifiers to do this.  Would one ever use multiple e type arguments?

Arbitrary order xparse e type arguments (embellishments)?

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