Good question.
On the blockchain it's the "withdraw permission" operation set, please check libraries/chain/include/graphene/chain/protocol/withdraw_permission.hpp for details.
withdraw_permission_create_operation
withdraw_permission_update_operation
withdraw_permission_claim_operation
withdraw_permission_delete_operation
It's not available on "official" GUI yet, nor dedicated commands in CLI yet (unfortunately). However, with CLI, you're always able to build transactions with the "transaction builder" command set.
begin_builder_transaction
add_operation_to_builder_transaction
set_fees_on_builder_transacction
sign_builder_transaction
Also you can do it with @xeroc's python-graphene-lib tools.
I haven't enough time to write a detailed instruction right now. If you really need that, feel free to contact me.
Thanks so much! I will sure get back to you at a later time. :)