Hi. I want to make a video simulating the warm light of a fire, like this final scene from Freddy Fazbear's Pizzeria Simulator. How can I do it with Kdenlive?
https://youtu.be/ocbAfuNRQ1c?t=133

You have to sell your soul to the demon and he will help you out.
Just kidding

OK, it's very easy but also a lot of work, there is no simple button to press... I will give you a north:

Load your video
Create a Color Clip (whatever color)

Track 1 - Your video

Track 2 - BG Light

Bring the solid color clip to Track 2 and add a Cairogradient with this settings:
Pattern - Linear
Start Color - Black
Start Opacity - 0,000
End Opacity - 1,000
Start X - 0,500
Start Y - 1,000
End X - 0,500
End Y - 0,500
Offset - 0,000
End Color - Orange
Blend Mode - Normal

I also add a Distort Effect(Amplitude = 80, Frequency = 80), just to give some distortion and some movement in the background.

Add a composition to Track 2 and change the comp to Cairo Blend (Comp Track = V1, Blend mode = Add)

Track 3 - Omni Light

Take the same Color Clip and bring to Track 3. We are going to use two Cairo Gradients:
First -> Cairogradient
Pattern - Radial
Start Color - Black
Start Opacity - 1,000
End Opacity - 1,000
Start X - 0,500
Start Y - 0,500
End X - 0,750
End Y - 0,500
Offset - 0,000
End Color - Orange
Blend Mode - Normal

Second -> Cairogradient
Pattern - Radial
Start Color - Black
Start Opacity - 0,600
End Opacity - 1,000
Start X - 0,500
Start Y - 0,500
End X - 0,650
End Y - 0,500
Offset - 0,000
End Color - Orange
Blend Mode - Add

Now add a Transform Effect, we are going to use it to change the size, position and animate(opacity) the Omni Light

Add a Cairo Blend (Comp Track = V2, Blend Mode = add)

Track 4 - Repeat as many omni light as you want

Keep creating new tracks and using the same omni, use the Transform to change the size and have some variation, also every Omni you create must be Comp at Track V2 the fire background and only the BG track is comp to Track V1 your video.

I have no time to make a video tutorial right know but if you fallow this steps it will open your mind to what you want.
Maybe it helps a little more: https://i.postimg.cc/WbtqBDqq/kdenlive-light.jpg