Just create a 3rd sequence, and drop the other two sequences onto the timeline. They will look like any other clip that you can click, drag, trim, etc, with two exceptions….it’s a different color and if you double click it, the sequence timeline opens rather than loading into the viewer. This is called nesting, and is used to simplify a timeline that has some intricate parts, especially those with lots of layers that can accidently be bumped a few frames/seconds and throw things off.
To apply filters, use motion controls, etc., right click the nested sequence on the timeline, and select “open in viewer”. Or hit the return button on the keyboard. Now you can manipulate the scale of the entire sequence or apply color correction without having to adjust each clip individual.