While the files you choose to delete remain in the Collector, you can feel pretty safe and change your mind any time.
But ultimately, after clicking Delete button and the 5 seconds countdown, DaisyDisk will permanently remove those files and folders, so that it will not be possible to “undelete” them. Note that DaisyDisk doesn’t move the files to the system Trash, because in that case, no disk space would actually be recovered.
If you have accidentally deleted some files and want them back, there are some “undeleting” tools in the market, but they do not guarantee anything. You may be lucky and have your files back, or you may not.
If the files are really important to you, we recommend to immediately turn your Mac off to prevent overwriting of the deleted files and hand your drive to a local professional data recovery service. Their chances are much higher.