As there were several posts requesting something that allows pre-setting filters on inserters, I decided to combine the ideas in a single post.

I have ideas in mind that could handle this request, and would like to get comments from users before implementing.

There will a toggle, whether a toolbar button, a held hotkey, or if robust enough, a mod setting, which will enable "smart pre-filtering", which will work as follows:

• An inserter pointing towards a belt/chest, will set a filter according to the outputs of the source and the items on the belt/chest. For example, an inserter pointing towards an ash belt will be set to ash. Research would be needed to see if we can filter by the drop lane.
• An inserter pointing towards a belt/chest, where a different inserter from that entity is already filtered, will be filtered by "what's left". For example, if another inserter filters ash, and this inserter is pointing towards a non-ash belt, it will be filtered by "not ash" or by the specific items.
• An inserter from an entity with multiple different items, pointing to anything other than a crafting machine, will be filtered to "whitelist". This is for entities such as platform hubs, landing pads, big mixed warehouses.
• An inserter pointing towards space will be filtered to "whitelist".

While it could be nice to change filters after the the inserter was placed, according to changing conditions e.g. a belt/assembler is removed, this can cause more chaos and would probably not be good.

I'm not entirely sure how the options you described would work in practice.
Maybe we could work the other way around? If a manipulator directed from a source that contains multiple items, such as a conveyor belt, chest, or workbench, automatically checks the "use white filter" box but doesn't set any filter, we'll avoid the situation where the manipulator immediately picks up any item until the user specifies which item it should pick up.
Example #1: A chest contains 4 items. Currently, the manipulator picks up any item, or an item based on some internal logic (possibly based on its name, I'm not sure). So, in order for the manipulator to be able to pick up the item I need, I need to specify it in the filters, but the manipulator has already picked up some item after placing it.
Example #2: The feed contains two items, ash and wood. The manipulator will now grab the first item it encounters, and only after I set a filter will it grab the ash.
However, if the manipulator is set to whitelist mode but without a specific filter, the manipulator will not grab the first item it encounters and will wait for the user to specify which item to grab.
That is, we will avoid situations where the manipulator, having several items in the source, takes whatever comes to hand, and the user will not have to deal with cleaning the manipulator itself, the tape, and so on from what the manipulator has already managed to throw there.

Yeah, I see in the discussions that there was already a suggestion about the same thing. I also think it would be easier if the installation happened this way, with a hotkey, or by default if there are two or more items in the source.