I've had similar experiences with GoPro Studio, and it's unfortunate that it's no longer available. Have you tried using Adobe Premiere Pro or Final Cut Pro X? They're both professional-grade video editing software that may take some time to learn but offer more flexibility and control over your footage. Alternatively, you could try using online video editors like the one at https://www.movavi.com/add-text-in-video-online.html. I've used it to add text to my videos, and it's quite user-friendly. You could also try editing your footage on your smartphone using apps like Adobe Premiere Rush or InShot.
