On-Request Texture Buffers / Shader multi-pass & buffer access

[Stealthii]

I really appreciate the FFT source support. A feature I'd like to see is access to additional buffers we can write to, and retrieve in additional passes, in order to build more complex effects like the following examples:

https://www.shadertoy.com/view/3lKSz3
https://www.shadertoy.com/view/4tGfRd

In order to reduce development complexity, having access to the following on-request buffers would be a nice feature:

uniform texture2d image_previous;                 // previous frame of the source texture (same frame or blank if initialized)
uniform texture2d target_previous;                // shader output from the previous frame (as above)
uniform texture2d builtin_texture_source_<NAME>;  // selectable OBS source to use as additional texture

With access to additional sources, and previous pre-FX and post-FX texture buffers, most of the complex shader chains could be built using source mirrors and shader chaining.

[HeyItsLollie]

I discovered tonight that I couldn't create my own uniform texture2d PreviousFrame; to attempt this manually, with SF+ returning the error "Textures as effect params are not yet supported." Hope this gets implemented soon!

[OvermindDL1]

It would also be very useful to be able to load a custom texture into the shader from an image file.

[MarioMey]

I also want plugin to have these features. I would want to recreate:
https://www.shadertoy.com/view/XsdGWj
https://www.shadertoy.com/view/Xs3GW2
Or maybe: https://www.shadertoy.com/view/Msd3W2