Default user name in ESS job parameter LOV

Summary:

We have created custom ESS job to invoke OIC integration using datamodel type - http. We need to pass logged in user's user_name as query parameter to integration call. Please suggest if we can default user_name in ESS job parameter so that we can pass it to integration without manual intervention. PFA screenshot where we need to add default value for user name parameter in ESS job definition.

Note: ESS job user_name parameter is created as LOV and 'fnd_global.user_name' is used in the query. This is restricting LOV values to single value i.e., logged in user's user_name but default value cannot be set.