I have seen so many variants of this since 2010.
OpenStreetMap need a standard for tagging shops that are offering parcel services, manned, or un-manned.
This is a problem that been around for a long time, discussed in many forum threads, but I can still not find an official tag standard.
International parcel operators have historically always delivered directly to customers, but times are changing, and there needs to be a tag for the new “pickup points”. Manned or un-manned.
Some background from my country:
In Sweden regular post offices are almost gone entirely. Instead postal services are available in many different types of shops. Supermarkets, Tobacco stores, Candy stores. And with same opening hours as the “shop=”. Same staff. NEVER the postal operators staff, never with own opening hours for the parcel service. There is even a new type of pick-up service available on some locations, which is a “fusion between a shop and pick-up-point” called Leveriet (a made-up-word, maybe “Ship-n-Store”). You get your parcel, try your goods in a personal cabin, keep it, or directly return it to sender.
And because the lack of wiki-standard for tagging this, shops are in a risk of vanishing on openstreetmap shops in Sweden, because people re-tag shops as “amenity=post_office”. Or there is a risk the map will never have correct tags on where you can send/receive parcels. And this in times where more and more buy stuff online. Need to return parcels to shops online, etc…
A common suggestion of solving this situation has been to place two nodes, where one is a “amenity=postal_office”. But first: it is not an Amenity, these pickup-points are “a-part-of-a-store”. It is the shop employees manning the pickup-point, with the exact same opening hours. Secondly: Not all postal services are available. And lastly: For us users editing opening_hours, etc, this will create duplicate work, updating two nodes. 
At least in Sweden one of the most common questions customers have when they know a package is available for pickup is: What opening hours do the shop have that has the pickup point?. The parcel operator says: Ask the Shop (because the pick-up-point is not theirs).
Again: I think there is a need of creating a tag standard for nodes with “post_partner/pickup” services
According to tagfinder.herokuapp.com there is a tag “post_office=✱”, to be used “for post offices in a store”.
(https://wiki.openstreetmap.org/wiki/Key:post_office) ← which is empty
Someone with knowledge about proposing a new tag in wiki should create a well written proposal, and let us in forum know about it (so we all can vote).
I do not dare do it as a newbie, because I have learned that when the vote is done, the case is closed. Like forever.
My proposal (so far, and based on both German and French variants seen in other threads):
shop=supermarket
brand=Lidl
(post_office=yes) -> so widely used so can't probably take this away
post_office:services=letter,parcel,stamps
post_office:type=post_partner
post_office:operator=Deutsche Post|DHL|Hermes|TNT|...
So lets brake the above down if it works:
The main shop is a “supermarket” in this case, and this is what the signs on the street say. At most there is a small sticker in the window saying something like “DHL”. At least in many parts of Sweden.
A “brand” should not be mistaken for what it is a brand for → Check
Is this a post_office → Sometimes, so could be useful if more specification is then added
So what is the situation going inside the shop?
When you enter the shop, there is a manned desk where you can send/receive parcels from one, or two operators, or sometimes (not always) an official post_partner for that country. Stamps are not always available to buy, it needs to be defined. → Check
Is this an official postal partner? → Tag for that too → Check
Although: Lately more and more “self-service-boxes” are being put INSIDE shops. So these tags need to be flexible, but rock solid. So maybe the tag postal_office:type needs expansion to things like “vending_machine”. Although quickly you end up with possibility for multi-value. Not sure if that could be allowed.
Last tag is important if you know which operator you know is delivering to you. But I feel that a parcel “operator” should be able to be tagged, without the “demand of being a Post Office”. So not a perfect fit, but good enough if this tag is ALWAYS used (if updating from open sources by script)
And the above suggestion would need updates to the following pages:
https://wiki.openstreetmap.org/wiki/Key:post_office
https://wiki.openstreetmap.org/wiki/Key:post_office:services
https://wiki.openstreetmap.org/wiki/Key:post_office:type → exists when writing this post
https://wiki.openstreetmap.org/wiki/Key:post_office:operator
Although the more I think about it (writing this down matures my thought) is to maybe even complement the vending=parcel_pickup, to maybe something like parcel_pickup:type=vending, and then tag other main tags (like shop=, amenity=) with tags showing it is a pick-up-point for parcels. Because I do not see why you from a customers point of view would care if it is manned/un-manned as long the opening hours are the same as the shop you are entering. Which would change my suggestion to a completely new tag:
shop=supermarket
brand=Lidl
parcel_pickup=yes
parcel_pickup:services=letter,parcel,stamps,customer_rooms
parcel_pickup:type=vending or manned
parcel_pickup:operator=Deutsche Post|DHL|Hermes|TNT|... <- multi-value accepted
Summary what I want help with in this thread:
What are the steps of getting ONE official “tag definition”/way in OSM-wiki for all these parcel pick-up-points which are located in another amenity/shop?
I mean: The answer could be that you always need to define
That happened mainly in really rural areas (think northern Scandinavia or alpine regions, where the same POI is often also bus/train ticket office and/or food shop) where many services have of course not 
to be bundled to attract sufficient amount of customers per day to pay off the employee’s wage and the infrastructure, but just and only to make OSM tagging more challenging 
) After the federal post office was privatized, the resulting state bank still belonged to the new “Deutsche Post AG” and was only later sold to another bank.