I do know that you must use the Skyline administrator install with DIA-NN in order to be able to use the "Skyline" button.
I am not sure exactly what that button does.
DIA-NN 1.9.1 now produces two different .speclib files, one of whose name ends in ".skyline.speclib".
Skyline only knows how to read the .skyline.speclib file-- the other .speclib file is in a new format that Skyline does not understand.
From my testing, it looked like a couple of things needed to be true in order for the .skyline.speclib file to be created:
1. The "MBR" checkbox is checked
2. Two or more mass spec data files (.raw, .mzML etc) have been searched
3. You are starting from a .speclib file (that is, the thing in the textbox next to the "Spectral library" button is a file whose name ends in ".speclib".
If all three of those things are true then you will end up with a .skyline.speclib file.
You can then use that file with Skyline by using the "File > Import > Peptide Search" menu item.
That is how we have been using DIA-NN 1.9.1 with Skyline in our lab.
If you would like, I could try to figure out how to get that "Skyline" button to work in Skyline.
It would be helpful if you could send me the files that you are searching with DIA-NN so that I can try to get it to work on my computer.
You could zip up all of your files and upload them here:
https://skyline.ms/files.url
-- Nick