A few users have reported that any Malleable VIs (.vim files) in your project will not appear in Quick Drop like other project files do. This has been reported as CAR 665190 and should be fixed in LabVIEW 2018 and later.
For now, to fix the issue locally on your machine, follow these steps:
1. Copy the file attached to this post to your [LabVIEW 2017]\resource\dialog\QuickDrop folder. Backup the existing file if you wish.
2. Mass compile the [LabVIEW 2017]\resource\dialog\QuickDrop folder.