Hi Erik,
This was an original feature requirement of the Edit iRT Calculator form, because the Aebersold lab had accumulated so many iRT values already that we wanted to make it possible for them to just paste into the form. I don't think we have broken this, and that you can still click on the grid and use Ctrl-V to paste a 2-column list of values from Excel (or just tab-separated from a text editor).
Let us know if this is not working for you, and we can look into what you are doing further. Otherwise, I would expect this to work with Ctrl-V to paste.
Good luck with your research. Thanks for posting to the Skyline support board.
--Brendan