Because we have so many parallel lifetimes, typically, are these lifetimes being experienced by different soul extensions than the one in the current life?

The lifetimes we are talking about all pertain to you. There can be other beings and many of them branching from the soul itself on various other adventures because of the vastness of the soul and its potential, but for the purposes of dealing with your life, its meaning, and its karmic implications, all of the parallel lifetimes we are discussing, and have discussed with you, pertain to your very soul extension alone because that is what is of direct relevance to you. It is only those lifetimes you experience as the part of you in the current physical life that are interrelated karmically in the same way, meaning "a more direct cause and effect and an assignment of responsibility." In the same way that you are a separate portion of the soul on this journey, what you do or do not do will not cause harm or benefit directly to other portions of your soul engaged in other business elsewhere and vice versa. So you will not inherit any of their karmic penalties and are on a kind of separate track of experiencing. They have a similar situation with the spiraling of time being a factor in their progression in the adventures they take on and the lifetimes they create in a similar fashion. So the parallel lives are all yours that we speak of and are being formed as a decision that can happen at any moment to start a parallel lifetime going. This will always be for some strategic purpose to add to the experience so there will be due regard for careful planning—where you will be going and who you will be among and what objectives are in mind to accomplish with the key milestones of that life experience. Many times this will be a reworking of something already experienced that needs to have a counterpoint for growth purposes and to rework the karma in a helpful fashion. So your karmic burdens are not all on hold waiting for you to get around to them. You are working on them in parallel, but inevitably more will be created to some extent as that cannot be avoided, especially in the physical realm with its limitations and challenges.