What I always do is I have my yellow belt production that outputs into a chest which is then used for red belts. Then if you upgrade that chest to a yellow chest, the yellow belts from your trash slots are automatically put into it, you don't even need to set a filter.

But yes, if you are using bots you need a circuit condition so it doesn't use all of the items in the chest. To do that you only need a singular cable though, you directly connect the chest to the red belt inserter. Still the option I would recommend. Looks really clean.