We have various places collecting more popular and more useful tags.
- taginfo (counting popularity in database)
- iD presets
- Vespucci presets
- JOSM core presets
- JOSM external presets (multitude of them)
- OSM Wiki
- NSI
- Organic Maps editor preset
- Organic Maps display
- CoMaps editor preset
- CoMaps Maps display
- OsmAnd display
- display/processing in various proprietary data consumers where we have no good way of getting what is supported
- what else?
There are some attempts to synchronize between them and to automatically detect likely missing parts.
- GitHub · Where software is built - high use tags missing from iD presets
- sync NSI tags · Issue #362 · openstreetmap/id-tagging-schema · GitHub - tagging used by NSI missing from iD presets
- https://github.com/osmlab/name-suggestion-index/commit/f0c65c8dbdac22a2c37c0fcccaf143ab0cc1f112 - NSI detects popular shared POI names that are likely brands, generated monthly by some scrip (or maybe it looks at brand tags?)
- possible extensions for AddOpeningHours, AddWheelchairAccessBusiness, AddPlaceName · streetcomplete/StreetComplete · Discussion #6402 · GitHub - iD places missing from SC quests
- Frequently used keys without wiki page | Reports | OpenStreetMap Taginfo - high use, missing from wiki (this one basically lists various import debris that has no good reason to exist)
I remember that JOSM used to detect high use tags (or keys) but I cannot track it down. Maybe they stopped doing this?
And there is also obviously a manual process of people filling issues about lack of support, which is more likely to happen for popular tags. Maintainers may also look at taginfo or simply notice new tagging not supported yet.
I have a feeling that more of such cross-checking would be helpful.
(though feel free to tell me why it would be a waste of time)