Do you think you could expand the warning for wrong items in filtered chests, such that it can warn you for when an item is in an UNFILTERED chest when there's a filtered chest available somewhere else?

An example would be when you set up a yellow chest, add a filter, then any item that matches this filter that already exists in other chests in the network should get flagged for the warning. Sometimes If i deconstruct parts of my bot mall to relocate for example a blue belt assembler, then the belts will get deconstructed into a generic yellow chest. Then when I set back up my assembler blueprint, which has a filtered chest for the blue belts, I'd want the old belts to get moved back into my new filtered chest.

That is something that would be possible, but I'd have to think about whether it could be done efficiently as well. All of the storage-suggestion logic runs in a single pass, where it looks at each storage entity one at a time and does all the processing there. For this, I'd need to remember a list of every filter and every item stored anywhere and do a comparison at the end; that could be quite expensive for both storage and compute.

It might be worth it if it is something most users would want. Anyone else think this would be useful? :) I could of course add an option, but I prefer to keep those to the minimum.

What about a manual button to allow doing a one time scan for these chests, so that you can just click the button and it'll mark the items for deconstruction inside the chests, which means bots will automatically move them to a filtered chest if there's space.
Essentially, a "mark unfiltered items for deconstruction."

That would be taking actual action, rather than suggesting something you might want to do - not something I do today, but could of course be possible. You could argue that the current filter suggestion could allow you to click the suggestion and mark all of the mismatched items for deconstruction too :)

With your new suggestion, I'd also need to keep track of the amount of space available in filtered chests, to make sure there is enough room to move everything that is in unfiltered storage (but could be in filtered) would actually fit somewhere filtered. As I think about the details, it feels a bit messy, don't you think?

Right I see the problem. Though it certainly would be nice if it was possible to know when items are not in their filtered counterpart! Mainly just an OCD thing I guess, but sometimes if you're producing something based on amount in a chest, and that item already exists in the thousands somewhere else, would be nice to be able to merge it all together lol. Right now I'd have to manually open up the remote view logistics menu (hotkey L), search for an item, then click on them to see where they are stored and then go manually mark them for deconstruction so that it gets moved. For every item.

That sounds tedious! Let me have a think about it :)