Unfortunately, there is not a way to change this so you default to Machines (View Composer Details)
However, this is something I have heard from customers and I can/will share this feedback internally to our developments teams and perhaps it will make it into a future release of the product as a 'Changeable' feature.
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Joe Graziano
Senior Solution Engineer - EUC Federal
VCP7-DTM, VCP6-DM, VCP6-DCV
vExpert, vExpertPro
jgraziano@vmware.com