File icon changes when dragged to DT 3.8.2 on Monterey Intel based

Hello,
i have dragged some PDF files into a year / month group structure in my DT database. When dragging PDF into the group, it gets created and for half a second it has a matching icon for PDF. Then suddenly changes to a white square. It could be some mini preview but my eyes are not good enough to tell. Is this a intended desire and is it configurable? I kind of would like to stick with the original PDF icons.
Kind regards

This should be a thumbnail of the first page (assuming the PDF option is enabled in Preferences > Files > Thumbnails)

ah, oh then i recognized it correctly… i switched it off, but the ones created already remain, is there a way to remove the thumbnail?
Kind regards

Sure, see Data > Thumbnails > Remove

Hello,
thanks so much for sharing and your patience, now got access to the translated options within the manual, there are just so many options…

Kind regards