A method for installing an accessory onto a pipeline to be laid on the seabed, includes launching the pipeline from a first position of a tower in which the tower is at an angle α with respect to the vertical; stopping the launch of the pipeline, and hanging off the launched pipeline in a hang off module; positioning an accessory in a tower firing line; attaching the accessory to the launched pipeline in the hang off module and to at least one A&R cable; suspending the accessory and the launched pipeline from an A&R system; disengaging the hang off module from the launched pipeline; pivoting the pipeline launch tower to an accessory launch position in which the tower is at an angle γ that differs substantially from angle α, such that a pipeline launch trajectory is created which is large enough to launch the accessory and the launched pipeline with the A&R system.