You can use advanced keyframes to achieve this effect. They give you full control and the possibility for setting start and end points. Just press the stop watch and activate the keyframes panel with View > Keyframes or Ctrl+7 (on Windows).
Well what I found confusing is that when you enable Keyframes on a filter, there’s no obvious way of adding another keyframe… I don’t know why there’s not just a button next to the “Set simple keyframe” buttons to add another keyframe
I ended up finding out that clicking that circle in the viewer at the time you want will create a new keyframe at that point, but I only found that out by finding a different reply on here
I understand that this can be confusing. The logic seems to be that a keyframe is added automatically if you change something, so either by moving the rectangle or typing a value.
An advantage for this behaviour is that one does only have to place the playhead and change a value instead of placing the playhead, changing a value and then pressing a button.
But I agree that a separate button for adding keyframes as an option would be helpful.