Here’s what I did. I have a video for the first play that lasts 17 seconds and links to the main menu. To create the main menu I took a snapshot of the last frame and used that as the background of the menu.
That way the video plays at the beginning only and the buttons appear at the end. When you go to a sub chapter and return to the main menu the first video does not play.
I experimented and was able to get good results by replacing media and saving themes. Instead of importing new media I replaced it the media properties.
Try FX, Sony Color Curve. To increase midtones, double click on the center of the line to create a point. Drag it diaganally to the upper left. To decrease the highlight drag the upper point down.
Place each video on a separate track. Mute the audio on one of the tracks so that only one is heard. Place Envelopes on each track and raise & lower the levels on each video track as you switch back and forth. Place keyframes to control this.
Watch this: https://www.sonycreativesoftware.com/keyframewebinar