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ls /usr/portage/profiles/funtoo/1.0/linux-gnu/mix-ins
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outputs :

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README gnome media server-db server-web workstation-minimal
dvd kde rhel5-compat server-mail workstation xfce
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We can see a folder named xfce. Somehow

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eselect profile list
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doesn't list that folder. Example :

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Currently available arch profiles:
[1] funtoo/1.0/linux-gnu/arch/x86-64bit *
Currently available build profiles:
[2] funtoo/1.0/linux-gnu/build/stable
[3] funtoo/1.0/linux-gnu/build/current *
[4] funtoo/1.0/linux-gnu/build/experimental
Currently available flavor profiles:
[5] funtoo/1.0/linux-gnu/flavor/minimal
[6] funtoo/1.0/linux-gnu/flavor/core
[7] funtoo/1.0/linux-gnu/flavor/desktop *
Currently available mix-ins profiles:
[8] funtoo/1.0/linux-gnu/mix-ins/dvd
[9] funtoo/1.0/linux-gnu/mix-ins/gnome
[10] funtoo/1.0/linux-gnu/mix-ins/kde
[11] funtoo/1.0/linux-gnu/mix-ins/media
[12] funtoo/1.0/linux-gnu/mix-ins/rhel5-compat
[13] funtoo/1.0/linux-gnu/mix-ins/server-db
[14] funtoo/1.0/linux-gnu/mix-ins/server-mail
[15] funtoo/1.0/linux-gnu/mix-ins/server-web
[16] funtoo/1.0/linux-gnu/mix-ins/workstation *
[17] funtoo/1.0/linux-gnu/mix-ins/workstation-minimal
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Therefore it's not possible to add xfce profile.