Adding and removing keyframes is very similar to Adobe After Effects.
Click on the
+ icon (on the left of the property name) to add a keyframe. Once added, this icon changes into a
x icon. Click it again to remove the keyframe.
As you can see above, it's possible to select a keyframe and move the ticker back and forth to see what the outcome will be in the past or future. The
xicon tells you that you've selected a keyframe. Changing the value here will change the value of the selected keyframe and doesn't create a new keyframe at the current ticker position.
When you move the ticker position, the
+/x icon tells you the presence of a keyframe for the current time. You can also select a keyframe by clicking on it. Once selected, you can move the ticker ahead in time of the keyframe and the
x icon stays visible to inform you that you've selected a keyframe. Pressing this icon removes the selected keyframe.
Alt key and drag a keyframe to duplicate it.
Right click on a keyframe to copy it, or select the keyframe and hit
Command+C. Move the ticker to a new position and hit
Command+V to paste it.
Multi-selecting keyframes is not implemented at the moment, will be added in the near future (on the backlog).