How to start and end an animation assigned keyframes sorry if this has been asked already, but how do you make an animation start and end at first and last assigned keyframes rather than specify a frame number for the start and end frames separately?

While working on my character animations, I always end up changing the scale, adding extra elements, etc. of my animations and it's always a bother to go back to the timeline window and set the start and end conditions to what I want. Is there a more convenient way of doing this?
Use the "preview range". You can call it via P:



It will set a temporary play range, which you can toggle with this little clock icon near the start/end frames: