It'll be nice if you could record voiceover in kdenlive more easily. That could be solved if there was a record-button beneath the video screen which you can click and select a microphone from a list and easily record your voice comments so that they are pasted in the timeline.
It’s on the whishlist for Junior-Jobs: https://phabricator.kde.org/T9292
With version 18.12.1 screengrab with audio is fixed. Please have a look. Voice over is on the task list: https://phabricator.kde.org/T10314 (Bug 367676). We closed this bug. If it still appears in the latest version, please feel free to re-open it and update the affected version number.