Your queries

This project started out for southern Africa, but is now international.
Anyone is welcome to use it, and the associated observation fields.

If you want to look at a specific region, that filter the data.
But usually one wants to filter by taxon.

e.g. https://www.inaturalist.org/observations?place_id=any&project_id=undescribed-species-and-taxa&taxon_id=47157&verifiable=any
For most meaningful results, download the data with the field: "New species reference and name:"

No!
That is just a project (in fact, 2 projects):
https://www.inaturalist.org/projects/undescribed-species-on-inaturalist
https://www.inaturalist.org/projects/undescribed-species-on-inaturalist-umbrella
and there is a third (just for spiders):
https://www.inaturalist.org/projects/undescribed-arachnid-species-found-on-inaturalist

But these are totally inadequate.
Our project, contains several features, the most of which is to allow entry of these fields:

Observation Fields
• New species reference and name
Please give a reference for the species (e.g. Cape Plants II Disa sp. 4) or a herbarium specimen number
• Range extension documentation
Please estimate the distance of the range extension and your source for justifying this.
• Unusual forms and variants
Please use a logical form and see what others have been using for your species
• Specimen Herbarium/Museum Voucher Number: (CREW)
Your personal accession number for the specimen collected. (leave blank if none - do not include if none)

Whereas the other are merely projects, this project allows one to filter new species: for instance:
Here are the records of the undescribed species, which we are calling "Indigofera rodinii"
https://www.inaturalist.org/observations?verifiable=any&place_id=any&field:New%20species%20reference%20and%20name=Indigofera%20rodinii%20sp.%20nov%2e

One can to the same with the other fields, which makes this project useful, where the others are merely one-dimensional.