OK, fair enough. Are you aware of other trials in our system where new evidence can't be introduced?
The Senate is LIMITED to consideration of only that which comprises that article, not anything extraneous to it, which certainly any "new" testimony or evidence would be.
I don't see where you get that from the Constitution, which is famously vague on the impeachment process.
Why would the sole right to try a case preclude new evidence? That's not how any other trials work.
The Constitution gives the power of impeachment SOLELY to the House of Representatives. To impeach, evidence and testimony is gathered, then formulated into an article of impeachment that the House must then present to the Senate for final judgement. "New" evidence would fall under the evidence/testimony gathering phase of an impeachment and not the final judgement phase that only occurs when the House presents an article of impeachment to the Senate. In this particular case, the House is the party responsible for developing any new evidence or testimony and formulating that into it's own article of impeachment. No one in the Senate can keep them from doing this just like no one in the house can force the Senate to do this. According to the roles of the impeachment process assigned to the House and Senate, the Senate cannot develop evidence, it can only judge an article of impeachment as delivered by the House. An impeachment is not like a normal trial.
Now, they want Bolton to submit to their illegal demands by using the Senate portion of the impeachment process to call "new" witnesses. If Bolton had a legal right to fight the original illegal subpoena, he certainly retains the same right to fight one that if issued by the Senate, would be an unconstitutional one. That legal fight would have to work it's way through the legal process and would take much longer than the Senate wants this to go on. I think this is really what the House wants, to tie up the Senate with this impeachment crap as long as possible.