A folder may take too long to open because Windows is processing thumbnails
for videos and pictures even if they are not needed for the file types not
related to both.
To solve this, go into any folder especially the parent or root that has
many folders in it. In this example I select Download folder.
Right-click on any blank surface in the folder and choose
Customize this folder.
In the Customize tab, under Optimize this folder for: select
General Items and check or tick the box Also apply this template to all subfolders.
Click Ok to save.