For doors that go between scenes in no signal, I've had this pattern of creating an extra pair of animations to easily switch to the open or closed state of a door, for a total of four animations:

• open - The open animation
• close - The close animation
• opened - A single frame which sets the door to the opened state
• closed - A single frame which sets the door to the closed state

Setting up this extra animation is tedious, but it was something I did because I wasn't sure how to play the last frame of an animation. However, when I was implementing the ability to save and load the state of other doors in the game, I found out that many of them don't have an opened and closed animation and I was reluctant to make them, so I explored how to do it again.

As expected, the paths that I probably tried before didn't seem to work in Godot 4.3.stable.

The following attempt fails, because it still plays the opening sound despite the fact that update_only is true. I suspect this is because the sound is played on the very first frame.

play("open")
seek(get_animation("open").length, false, true)

The following also fails, as the door fails to open at all:

play_backwards("open")
stop()

I thought this was because the play_backwards function didn't actually do anything until the next process, but manually requesting and update didn't work either:

play_backwards("open")
advance(0)
stop()

However, I noticed that the documentation for play_backwards mentioned that it was the same as play, but with custom_speed = -1.0 and from_end = true. This is very similar to what I want, except with a custom_speed of 0 since I don't want the animation to play. Calling the play function myself appears to work:

play("open", -1, 0, true)