You can click on your logistic auto-fetch feature and just have robots search all the boxes for the items you want, and they'll automatically refill your inventory to 300-belts.

And then when you build a belt somewhere, you can either choose from your inventory, or shift-click and/or blueprint build to have robots search for those items in your entire logistic network and they just fly out, find the item, come back, and place it for you. Just in like 2 or 3 clicks (or less).

So for a lot of these challenges and demonstrations, Factorio players aim for "belts only" or other such constraints, to try and force ourselves into design constraints. Belts-only also uses zero-power (bots need power to function, and its rather substantial in practice). So there's power-benefits to going belt-only.

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So what is your goal here? If its to build a tree in Factorio, I think we can say you succeeded.

But its not the optimal play or the "meta" factory design, lol. But I recognize that's not quite what you were going for. (Ex: the meta would be to just use bots in a bot-factory. Or keep items sorted in a belt factory, no reason to mix belts)

I think pushing players to think deeply about the "meta", including the deep thoughts upon how CLOS Networks apply to high-quality Belts/and/splitter designs, is very rewarding. Its not about trees though.

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Mixed-belts are fun though. And I think I spent many good hours and weeks thinking about them back in my Factorio days. Lots of interesting problems to solve, but I think my problem was that these solutions weren't meta, nor did they demonstrate any beautiful mathematical concept.

Benes Networks / CLOS networks applied to belts however, were a perfect match. The best builds were those that matched the deep mathematical/comp. sci foundation of Benes Networks. So it was the "more fun" part of Factorio to me. Not only was I learning some deep Comp. Sci topic, but when I improved my designs based on CLOS Networks, they instantly led to improved belt-balance and throughput in my factory designs.