Just a simple field "execute_after", that execute "entity_action" after self execution.

Just like that:
{
"type": "origins:active_self",
"entity_action": {
"type": "origins:add_velocity",
"y": 10
},
"cooldown": 100,
"key": {
"key": "key.origins.secondary_active",
"continuous": false
},
"execute_after": {
"entity_action": {
"type": "origins:execute_command",
"command": "particle minecraft:dust 10 5 5 0.5 ~ ~1 ~ 0 0 0 1 10",
"permission_level": 2
}
}
}

Or probably execute a passed power/subpower instead of a "entity_action"

You can use the and action (link) to combine multiple actions (they will be executed in order). If you need a time difference between the actions you want to execute, you can use a delay (link) action.