When you record screen simulations in Storyline, you only have to record your screen once, then you can reuse the same recording either as a video on a single slide or as a series of step-by-step slides.
Unlike the single-slide videos, the step-by-step slides cannot be resized. This means your simulations are baked into each slide. There's no way to resize or move the simulations to another part of the screen. If you want some additional space on either side of your simulations, you're going to need to increase the slide size after you record and insert your simulation.