There isn't currently a way to transfer your 1SE seconds from Android to iOS or vice versa. Video on mobile devices is super complex with varying codecs and formats. Right now we're focusing on getting accounts and backup to iOS users but in the future, we'd love to have it all under one house. For now, we recommend folks mash one final video on their old device so they can then edit it together with their new video.
If you're moving from an iPhone to iPhone, please read our backup and restore article here.
If you're moving from an Android device to another, simply log into your Google account 1SE is backed up to.