Implement nested filtering

[pavish]

Fixes #4803

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[pavish]

I finally re-started work on this PR, after it being idle for a long time. It's functional, complete with drag and drop.

2025-11-04.19-02-22.mov

However, I still feel like the UI doesn't quite look good. It might be because of the icons or the colors, or the lack of animation (I'm not sure what's bothering me).

@zackkrida @seancolsen @kgodey Please review the UX, play around with it, and let me know your thoughts.

If the UX looks good, I can cleanup the code and colors, and get the PR ready for code review.

[seancolsen]

Functionally, this works great, @pavish. Very cool!

Aesthetically, I agree it feels a little rough. And some of the rough nature of the design bleeds into UX challenge too. It wasn't immediately clear to me how to use it. I figured it out though.

Here's a quick stab at a slightly different visual representation:

Current:

Proposed:

What do you think of this?

(To be clear, I'm not proposing different colors — the colors are just taken from the last time I did some mockups which was before our app color changes.)

[seancolsen]

@pavish, here's another small UX suggestion. This one is less important, but I wanted to mention it because I think it would slightly improve usability, and it's possible it could make some of the UI implementation simpler.

This suggestion relates to the behavior when dragging an item. So it's somewhat difficult to mock up. I'll try to explain via text...

Currently, when dragging:

• The UI that follows my cursor is the entire thing I'm dragging. This can obscure the underlying tree of filter conditions, making it a little hard for me to see the place that I want to drop as I'm dragging.

• The filter entry that I'm dragging is removed from the tree. This makes it hard for me to understand where I'm moving it "from". It's a little harder to me to mentally retain my context.

• The drop target (the dotted outline) occupies space in the tree. This makes the tree layout change as I drag. That layout shift can makes dragging a little cumbersome sometimes. For example, if I drag 10px too far down, then I might need to go 100px back up to correct my mistake before dropping.

None of these issues are hugely problematic. After all, the patterns you're following here are quite prevalent across other apps. But with a complex drag-and-drop feature like this, I have a slight preference for the UI to basically "stay in place" as I drag.

I'd (slightly) rather it work like this:

• The UI that follows my cursor would be very small — just an icon, or even nothing at all. This way I could see the underlying tree more clearly.

• The filter entry that I'm dragging would stay in the tree but would get opacity 0.5 or something similar. This way I could see what I'm dragging and where I'm dragging it from.

• The drop target would be a blue line in between items, similar to the UX when dragging to rearrange columns. This way the layout would not shift around as I drag.

Not a big deal. But I wanted to suggest this. Who knows, perhaps you'd end up re-doing some of the DnD UI if change the layout to suite some revised aesthetic design choices, and perhaps the DnD behavior I'm proposing would be simpler to implement. I'm not sure. I've not looked at any of this code yet.

[pavish]

Thanks @seancolsen. I implemented the most commonly used UX behaviour for drag and drop, and filter groups. I do like your suggestions, however, I'll wait until Zack and Kriti have weighed in, before I make a call.