I have a folder for which a folder thumpnail is displayed in the properties. However, the icon of the folder is default.
I don't remember what I did to define the thumpnail in the properties. It was not my intention to assign a thumpnail to this folder.
How can I undo this in the properties.
In IMatch Help it is described that there is the possibility to assign a thumpnail to folders, but not how and also not how to undo it.
There is no need to remove it. If you delete the file used for the thumbnail, IMatch falls back to a default. You can also change it any time,
Unless you switch the Media & Folders to display folders thumbnails, you won't even see it. So don't bother.