It typically takes at least a decade, sometimes several, between first suspicions that something is a new species and it being officially named. During that time, the vocabulary used to refer to it is known as open nomenclature, but there are no absolute rules about how that should be applied.
Typically if the new species is very similar to an existing one, the abbreviation sp. aff. will be used. That’s short for species affinis, loosely meaning similar species. Thus, if it was suspected that the Ghanaian population of African bush elephants is in fact a new species, they may be referred to as Loxodonta sp. aff. africana while research is carried out to make certain.
Another abbreviation that is used in the same kind of way is cf., short for confer, and indicating uncertainty. Loxodonta cf. africana would refer to an animal that may or may not be Loxodonta africana.
One thing to avoid is using sp. nov. (species nova, new species) as this is not used to indicate a candidate new species, but rather reserved for the that time the species is being formally named.
Sometimes when a new species seems quite certain but more data still needs to be gathered before a taxonomist can formalise it, authors of a paper will assign a label, often based on the locality, something like Loxodonta ‘Mole National Park sp. A’.
If there is not an accepted label for the new species you are working with, then you could always establish one for your own use. As long as you explain clearly in the description of your observations, with any appropriate references, that seems to me a fine approach. You could say “the candidate new species dealt with on page x of xxx paper, hereafter referred to as Pseudexentera ‘ms. sp. LA1’.”
But as others have said, for the taxonomic ID, I would just ID it to the genus level and then use the description, comments and/or observation fields for your temporary species label.