If you feel the need to check Instagram while watching a movie, it might be that you’re watching the wrong movie.
If you feel the need to check your phone while in a meeting, it might be that you’re in the wrong meeting. Or meet wrongly.
If you feel the need to do other things while you’re doing one thing, it might be that that one thing wasn’t the best use of your time to start with.
Instead of looking for ways to re-use your time, it might be a better idea to use your time better in the first place.