How to change folder thumbnail?

[xnterone]

Is there any way to change what picture are shown as a folder's thumbnail ?

What I'm looking for is a setting similar to what can be done in Windows File explorer via:
Right click a folder->Properties->Customize Tab->Folder Pictures->Choose File

With the steps above, one can change the preview images of a folder in windows file explorer
Is there something similar in Xnviewmp ?

[michel038]

A first way : copy the photo you choose and rename it as "folder.jpg" in each folder
Other method : rename this photo "1.jpg" to make it stay first in alphabetical order.

But it's difficult to refresh folders thumbnails...
The only strong method I found is to delete the entry of the parent folder in "Settings, Catalog" screen, and then use "Import folder" button for the same folder.
But you must before be sure that you will not lose your categories, ratings, tags, ...
These data should be saved as metadata in the pictures...

[xnterone]

A first way : copy the photo you choose and rename it as "folder.jpg" in each folder
Other method : rename this photo "1.jpg" to make it stay first in alphabetical order.

But it's difficult to refresh folders thumbnails...
The only strong method I found is to delete the entry of the parent folder in "Settings, Catalog" screen, and then use "Import folder" button for the same folder.
But you must before be sure that you will not lose your categories, ratings, tags, ...
These data should be saved as metadata in the pictures...

Thanks so much for the answer,
Unfortunately the two methods you have suggested didn't solve my problem because of a certain condition I will explain below

You see, I have a folder, let's call this the top folder, which by itself contains no images but contains multiple subfolders that contains images
I want to change the preview thumbnail for the top folder with any image from one of the subfolders that contain the images
And to make things more complicated, I need the top folder to contain ONLY subfolders and must not contain any images.
So the methods you have shared are not the solution I seek. Thanks for sharing though

On Windows file explorer, I can solve all my grievances above via the method I referenced in my first post
But I don't want to do it with windows file explorer, I want to do it with Xnviewmp which is my preferred method to browsing and viewing images.
And I don't know how to do it in Xnviewmp, or if it's even doable at all sigh...

[xnview]

You see, I have a folder, let's call this the top folder, which by itself contains no images but contains multiple subfolders that contains images
I want to change the preview thumbnail for the top folder with any image from one of the subfolders that contain the images
And to make things more complicated, I need the top folder to contain ONLY subfolders and must not contain any images.
So the methods you have shared are not the solution I seek. Thanks for sharing though

put a file folder.jpg in this folder, and thumbnail will use this file (View>Rebuild thumbnails)

[harumscarum]

Rebuild Thumbnails not helping. Folder thumbnail not updating unless Thumb.db removed and XnView restarted. That issue was noticed years ago

[michel038]

Rebuild thumbnails works for me
- Select the parent folder in "Folders" panel
- Select the folder to refresh in the main area of the browser
- View > rebuild thumbnails