apologies if we’re not understanding one another, this stuff is complicated. I’m not sure if this will help or further confusing things, but this is how I would go about cleaning up Solidago and how that process leads into the questions about splitting.
Step 1: decide whether the goal is to curate in the direction of POWO or to deviate from POWO. Lets assume the goal is to curate in the direction of POWO since that’s definitely simplest
Step 2: handle taxa in iNat that are not in POWO
Step2a: internodes
POWO only has families, genera, species, and ssp/var so it doesn’t offer guidance on things like sections. I assume we want to keep them though so I accommodated them with a deviation
https://www.inaturalist.org/taxon_framework_relationships/464705
and included a link to a flag I made where the rationale behind these nodes and which taxa descend from them can be discussed (since we can’t refer to POWO here). There are also quite a few species not assigned to section or subsection that should be moved if possible (may not be possible).
Step2b: ‘relationship unknowns’
There are 55 Solidago in iNat that aren’t in POWO (and aren’t accounted for with deviations) we call these ‘relationship unknowns’. Assuming we’re not deviating, they can usually be dealt with by swapping them into other existing taxa (or in some cases new taxa that don’t yet exist that you’ll need to make). I usually deal with these first. (one caveat is that for some reason POWO often is lacking the nominate infraspecies e.g. Solidago curtisii var. curtisii - since we want these to exist on iNat, rather than swap these away its better to keep them and create not-external deviations to account for them)
Solidago araucana
Solidago arguta var. arguta
Solidago caesia var. caesia
Solidago canadensis var. canadensis
Solidago chilensis var. chilensis
Solidago curtisii var. curtisii
Solidago elongata
Solidago fallax var. fallax
Solidago flaccidifolia
Solidago gigantea var. gigantea
Solidago gigantea var. leiophylla
Solidago hispida var. arnoglossa
Solidago hispida var. hispida
Solidago hispida var. huronensis
Solidago hispida var. lanata
Solidago hispida var. tonsa
Solidago hybrida
Solidago lepida ssp. lepida
Solidago lepida
Solidago maheuxii
Solidago microglossa
Solidago missouriensis var. fasciculata
Solidago missouriensis var. missouriensis
Solidago missouriensis var. tenuissima
Solidago missouriensis var. tolmieana
Solidago mollis var. angustata
Solidago mollis var. mollis
Solidago multiradiata var. scopulorum
Solidago nemoralis var. longipetiolata
Solidago petiolaris var. angusta
Solidago petiolaris var. petiolaris
Solidago porteri
Solidago radula var. laeta
Solidago radula var. radula
Solidago radula var. stenolepis
Solidago rugosa var. rugosa
Solidago simplex var. ontarioensis
Solidago simplex ssp. simplex
Solidago simulans
Solidago spathulata var. gillmanii
Solidago spathulata ssp. glutinosa
Solidago spathulata var. nana
Solidago spathulata ssp. spathulata
Solidago speciosa var. jejunifolia
Solidago speciosa var. rigidiuscula
Solidago speciosa ssp. speciosa
Solidago uliginosa var. levipes
Solidago uliginosa var. linoides
Solidago uliginosa var. peracuta
Solidago uliginosa var. terrae-novae
Solidago uliginosa var. uliginosa
Solidago ulmifolia var. microphylla
Solidago ulmifolia var. ulmifolia
Solidago virgaurea var. praeflorens
Solidago wrightii var. adenophora
Solidago wrightii var. wrightii
Solidago × asperula
Solidago × bartramiana
Solidago × calcicola
Solidago × luteus
Solidago × neurolepis
Solidago × ovata
Solidago × raymondii
Solidago × ulmicaesia
Step 3. taxa in POWO not in iNat
there are 30 Solidago in POWO not in iNat. Assuming we’re not deviating and the goal is to make Solidago complete (ie add all the taxa to iNat in this clade), these need to be created.
Solidago argentinensis
Solidago calcicola
Solidago canadensis var. lepida
Solidago canadensis var. scabra
Solidago compacta
Solidago correllii
Solidago jejunifolia
Solidago kuhistanica
Solidago multiradiata ssp. paramuschirensis
Solidago nipponica
Solidago ontarioensis
Solidago ovata
Solidago patagonica
Solidago patuliginosa
Solidago polyglossa
Solidago rigidiuscula
Solidago spellenbergii
Solidago ulmicaesia
Solidago velutina ssp. velutina
Solidago virgaurea ssp. armena
Solidago virgaurea ssp. gigantea
Solidago virgaurea var. insularis
Solidago virgaurea ssp. jailarum
Solidago virgaurea ssp. kurilensis
Solidago virgaurea ssp. pineticola
Solidago virgaurea ssp. talyschensis
Solidago virgaurea ssp. turfosa
Solidago yokusaiana
Solidago × leiophallax
Solidago × maheuxii
Steps 4. Do we need to split anything?
Now the structure of the tree in iNat should match what we’re aiming for -that is POWO plus the deviation to accomodate the sections etc. But there’s still this question about whether adding any of the new species narrow what we meant by any of existing species and thus change the intention of existing IDs such that we need to split some of those existing taxa to replace those now ambiguous problematic existing IDs? If so we need to split.
For example, and back to your original example, did the fact that we added Solidago jejunifolia etc change the meaning of a lot of existing IDs of Solidago speciosa such that we should probably create a split like https://www.inaturalist.org/taxon_changes/86155?
Sorry if this just continues talking past one another. But that describes how I would go about cleaning up Solidago. If you can give another go to help me understand your issue, I’ll try again to see if I understand the problem and can help (or maybe better to be quite and let others help!)