The way I see it, there is a multiverse which is like an infinite collections of all possible space-time reality threads ... stretching from past to future ... and we have the ability to switch threads. Since each thread has it's own consistent past, therefore we are living/experiencing a new present complete with a different past (which already existed). So we don't change a past, we just experience a new Now moment which came with it's own past (and probable futures).
Julian Barbour (author of "The End of Time") considered the universe to be a collection of time capsules ... each capsule is a "Now" moment including its associated probable pasts and probable futures emanating from it. Manifestation is then the process of us experiencing these time capsules and ordering them in time based upon the beliefs that we hold. This is similar to the thread metaphor.
Lazaris draws a distinction between manifestation and creation. Manifestation is the process of popping 3D moments into our personal perception selected from a range of probable moments (something like Julian Barbour's metaphor). Creation, however, is the process of creating totally new possibilities. Since we have such an ingrained belief in linear time it is impossible for us to understand creation in the spacious present without thinking in term of causality, and linear time. It's perhaps a little easier for us to imagine preexisting probabilities in a multiverse that we're exploring ... but even that is impossible to fully appreciate.
Have fun with this!
“It is very difficult to explain, because what actually happens is sometimes so directly contrary to what seems to have happened. You do not simply change, or enlarge, your ideas or beliefs about the past – but you change the events of the past themselves for yourself, and sometimes for other also.
“It might help if you remember that despite appearances all events are basically subjective. Their “objectivity” happens at a certain point of focus, and as that focus changes, so do the events.”
(The Way Toward Health,Session January 12, 1984)