Use the priesthood line of authority of your current priesthood office.
You should always use the line of authority of the priesthood holder who ordained you to your current office. Brethren are instructed not use lines of authority from former offices they have held. The only exception to the above rule is that Bishops, Patriarchs, and even Apostles are instructed by the church to use the line of authority from their HIGH PRIEST ordination.
Example 1: If your father ordained you an Elder and he was a High Priest at the time of the ordination, your line of authority would go through whoever ordained your father a High Priest. However, if you were later ordained a High Priest by someone other than your father you will use the line of authority of whoever ordained that brother to be a High Priest.
Example 2: If your father ordained you an Elder and he was an Elder at the time, then your Elderís line of authority would be through the person who ordained your father an Elder. If, however, your father was subsequently ordained to be a High Priest, then your High Priestís line of authority would go through whomever the brother was that ordained your father to be a High Priest.
Our understanding at CenterPlace Enterprises is that you do not have several lines of authority that you retain as you progress through the Priesthood, but that each successive line of authority replaces the former so that you only have one line of authority at a time.
If you have any question as to which line of authority you should use, you can contact the Member and Statistical Records Department of church for clarification.