I have my reasons, why I don't make a transparent png image and add it into Godot. I want to animate the transparency.
How I can animate transparency a color-rect in Godot?
You can animate the transparency of the self_modulate or modulate properties using a AnimationPlayer or Tween to animate the transparency of a Control-based node. I've done this countless times for various UI fades.
11 days later
Good timing -- was just looking for this info! Thanks.