We have a verbal act of Trump asking for an investigation into Biden’s involvement in the investigation of Burisma. Now, if we did NOT have Biden on tape bragging about his own quid pro quo, that would arguably be impeachable. The question is whether there is a predicate for the requested investigation. If there is (and it spills from Biden’s own mouth), then Trump’s “verbal act” in not impeachable.
As to the transcript — all conversations between a US President and other foreign leaders are marked as Top Secret, Originator Controlled by default. (I work in this field of classification marking, by the way). This is both as a courtesy to the other foreign leader so he or she can feel free to openly discuss thing, and because an understanding to which the two might arrive at might then become the basis for strategic initiatives that adversaries should not know about.
Now, this idea that the transcript has been secured “where no one could see it” is nonsense. Because it is ORCON (Originator Controlled) it will be saved on a system designed for that higher classification, making it far less likely someone will see it and leak the contents.
And it is not the transcript that was declassified that was saved there; it was other transcripts of other calls between Trump and Zelensky. And I believe one of them was just recently declassified (in addition to the one that started this whole farce).