To create lexemes with QuickStatements, would you consider adding support for columns with "lid", "llcat", "llem" and "llang" headers?
Supposedly, "qid" can be used as column header if the lexeme exists, but if not, another option is needed, e.g. "lid".
"llcat" would be for the lexical category (an item), "llang" for the language (another item).
The lemma (llem) is a bit more complicated: It can be multivalued and language code needs to be supplied. Maybe a format similar to monolingual string could work. For creation, support for a single value would be sufficient.