A short hint in the form of an example or an addition to the in-game documentation on how to store/export op tags. I can't find information on this topic. It was not possible to obtain a practical result.

Please add this info to your mod page! This is literally the only info on this topic!

Also, some info on the Ingredient Buffer would be really good. I currently know nothing about this and can't find any information.

there is an in-game guide and all info you need is here. click the '?' button to open it

first you need to find out the tag of item/fluid you want to filter.
if you have kjs installed, you can use /kjs hand to see the tags of the item you are holding

then you input the tag to the input bar(the # doesn't needed) and it is all done

I would like to know how to add multiple tags to export/storage. They must have both Tags to export/storage.

I would like to know how to add multiple tags to export/storage. They must have both Tags to export/storage.

use | to add multiple tags. for example if you want to filter coal(forge:gems/coal) and iron(forge:ingots/iron), you need to input forge:gems/coal | forge:ingots/iron.