When I first installed Piwigo I searched that option for 30 minutes, in Piwigo admin panel, in google, in piwigo forum, in the extension list.
I could not believe it that such a complex software don't have this basic functionality , to set a album thumbnail if that album has only sub-albums. You can only set random photos from sub-albums as the representative thumbnail for the parent-album.

But later I found a workaround:
1) User gallery interface=>Parent Album=>Sub Album=>Photo you want as thumbnail=>Add to caddie

2) Administration interface=> Photos=>Caddie=>Select the picture=>Action=>Associate to album=>Chose the Main Album  (now that picture will be in both Sub-Album and the Main-Album )

3) User gallery interface=>Parent Album=>Photo you want=>Set as Album thumbnail (now the picture is set as a thumbnail for the Parent Album)

4) Administration interface=> Photos=>Caddie=>Select the picture=>Action=>Disociate from album=>Chose the Parent Album  (now that picture will be again only in Sub-Album)
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The Parent Album will retain the thumbnail as representative, even you dissociated from that Parent Album.

Last edited by eliz82 (2016-05-17 07:58:34)

An easier way is to view the photo you're interested in making the cover, select Edit then Photo Properties, scroll down to Album Thumbnail and then type in the album you'd like for the photo to be the thumbnail of.

(This is of course if I understood your request properly)

Thanks to jnashpiwigo. I was not aware if this feature.

Both solutions are working.

Very helpful!
Now if I could just post a durable screenshot to help show others...