I've collected all the questions and comments so far and here are the replys to them from our team. This post turned out to be quite a wall of text, but I hope it remains at least somewhat readable.

2 sections for the filter, why not. But having the possiibility to

take a basic filter as a base and change it to make a custom filter

would be great.

The idea was that the user could use these basic filters as a base to
custom filter. Think as if these built-in filters are just premade
custom filters that are fully customizable even further.

When you make a custom filter, allow to use it as a basic filter

inside (not as a base) a new filter (and allow to change the input

values).

That is why we applied the save and load function. User can load these
saved/previously used filters and modify/add something new to them.

activate/deactivate basic filters inside custom filters too.

Do you mean these eye icons? They are also in custom filter editor.

Create handy tools like rotate, resize, mirror,...

This is why we need user feedback :) these kind of functions didnt pop
into our minds.

How do I disconnect nodes in node editor? Just drag the arrowhead and drop

on free space?

Arrows are selectable like the effect icons. Just click the connection
line and press delete.

You mention input reordering for nodes. Will this be in a separate

dialog, or directly somehow embedded in the node editor? In case of

dialog, how do I distinguish for example two different inputs of the

same type? (I guess those will be labeled with original input numbers

and keeping the node editor still visible?)

By this we ment switching the inputs for a selected effect. We found
out that eg. composite gets two (2) input connections. If we swap the
connections we get a different output from the effect. This is why we
thought it should be easy to switch input order easily. This is shown
in the last picture in custom filter workflow. Inputs are numbered and
showed in connection view. This can also be seen in the same picture.

What about a possibility to add textual notes in the node editor

canvas or for used filters (i.e. tab "Notes" in the bottom)? I think

this can improve editing experience when creating complex filters

and/or editing after some time has passed.

That would be a good idea.

In your Added features section by "saving function of custom filters"

do you mean saving filters settings ?

We thought it would be great to save the whole filter including its
settings. For example.... user creates a filter which is created from
built-in vertical blur (the blur that can be accessed now from top
panel: Filters -> Blurs -> Motion blur vertical) and a self-made
custom filter. We could say the filter consists of these two parts.
User can then save this as a one filter which could be then used later
in other drawings by just loading it.

I assume the screenshots are mockups, but do you plan on also doing an

actual implementation? (At least of some of your ideas.) In either case,

have you thought about ways to overcome some of the technical hurdles?

In particular, you suggest to allow applying multiple filters to one

image. Do you have any thoughts on how to implement that in terms of SVG

representation? (If you also have ideas about how to reuse custom

filters in much the same way as filter primitives then I'd love to hear

it as well of course.)

Yes the screenshots are just mockups. We feel that we don't have
enough programming experience to actually implement these changes. We
thought about the technical difficulties while developing this idea.
We're not claiming to be SVG experts, but understood by reading
http://www.w3.org/TR/SVG11/ that it could be possible to include
multiple filters in a single svg file (see
http://www.w3.org/TR/SVG11/filters.html#AccessingBackgroundImage
example). This should allow separating the filters by filter ids.
After all... separating filter can be thought as applying them one
after another, right? IDs could simply be shown as filter name in the
UI. The problem is how to generate the connections from this svg file.
By this I mean how the effects are distributed at the canvas. The
current view is easier for this as they are shown as a waterfall type
view. Reusing these custom filter could be done by simply saving this
filter list as a single svg file. This file could then later on be
loaded if needed. It should open up the same way it was saved (filter
are separated and editable, parts can be deleted etc.)

As for the proposed interface, I'm not entirely sure I like the idea of

splitting it into a basic and complex interface. If the "complex"

interface is easy to use, why not make it the only interface? If it is

not easy to use, then that might be a problem. I do understand that you

don't always want open this huge window just to change a few things, but

I can also see different ways of solving that particular problem (for

example, instead of having two relatively unrelated dialogs you could

make a dialog that can "slide out").

By splitting the interface into two halves we thought it could be
easier for new users to familiarize themselves with filters and of
course easier using of these premade filters. At one point we had a
mockup in which these two halves are together. They were linked as the
loading is now in the basic editor. The active filter list is the same
in both views so it could be merged in this approach. The problem in
this vision was how to show filter parameters. And also this kind of
UI would fill the screen, which is what we wanted to avoid.

What I DO like is showing sample images, making filter "presets" more

accessible and of course a nicer filter editor. I also very much like

that you have taken the effort to do this kind of work, I might sound a

little critical above, but that's only because there is now something to

be critical about :) (Which is way, way better than having nothing.)

Constructive criticism is also welcome. Feel free to ask for more

information if needed :)

And please correct me if I understood this SVG standard completely wrong.