How to minimize the lines to edit in Adobe Audition?

That's a 6-channel file with only two channels used. Has it come from a Zoom device?

It looks like a stereo recording. On the extreme right of each channel, there's a track number displayed in blue. What you need to do initially is click on all the numbers you don't want (3 to 6) so that those lines turn white. When you have done this you'll have just the two lines in green. Now use Ctrl+A to select the whole of both tracks, and then use Ctrl-C to copy them into the clipboard. Now go to File>New>Audio File and in the dialog box that appears, create a new blank file. Now, if you go Ctrl+V you will paste those two file lines into the stereo file you just created, one on each of the two channels. Save the result - you've now got a stereo file you can edit, and as a bonus you've not destroyed the original file so you've got it as a safety backup.