Add-on: Quick Move Keyframes
With this add-on you can easily move all keyframes to the right or left from the current frame.
Blender.Fun writes:
Hi guys,
with this add-on you can save a lot of time, if you wanna have some space between 2 keyframes.
Just set your timeline cursor where you want to insert space, press Shift-I and all keyframes will be moved right or left (customizable).Have a great weekend,
Blender.Fun
No need to pay for useless add-ons.
You can select and grab, or select start and end and scale (S) to insert space between keyframes.