"Play file" does exactly what it is supposed to do, "play one file". To play whole folders you should use the third item in the Play submenu - "Folder".
In the beginning I had difficulty finding the "Play" option (as I don't understand what "window-shade mode" is). I didn't find it by right-clicking on an empty section of the Playlist, nor by right-clicking in the list, but by right-clicking on the tiltle bar of the Playlist Editor. I think "Play" should be available by right-clicking anywhere, and more importantly, "Enqueue file" and "Enqueue folder" should be there too.
I understand that everybody has different habits when selecting what to play, and that no menu structure will satisfy the majority. I find the standard file navigation tools in all programs cumbersome and ineffective (especially if one has to go through a deep directory structure). This is why I have long abandoned the supposedly "user-friendly" browsing interfaces of all programs and just use a separate file manager (Total Commander) to navigate and open my files, be it music, documents or work. Thus, if I want to play a folder (or enqueue several folders) in Wacup I just drag-drop them on the Playlist. Works 100% all the time and requires the absolute minimum number of clicks.
Um, did you actually read my post?...
Here, I'll quote it:
So, I first right-click on the playlist editor in window-shade mode, hover on "play", then left-click "folder". I navigate to the folder where the music is that I want to play. After I've selected the folder, I click "OK" in the open folder window. For some reason, it brings up the "open file(s)" window, which I don't want, because I want to play an entire folder of music.
In other words, when I right-clicked the playlist in window-shade mode (a.k.a. compact mode or whatever you call it when the UI for WACUP isn't in full, normal mode), I DID select the 3rd option ("folder") in the play sub-menu. I then navigated to where the folder was at in the "Add folder" window. I clicked OK in that "add folder" window. But, for some reason, that option didNOT play all the music files in the folder; rather, it opened up the "open file(s)" window instead, which is what I didn't want.
The thing is, I am able to select more than one file in the "open file(s)" window when I want to go that way as far as playing all the files in a folder. It just seems that, for some odd reason, WACUP isn't able to play all the music files that are in sub-folders within a main folder (which is how I have my music files organized; for Five Finger Death Punch, I have a main folder named for the band. Then, there are sub-folders within that main folder that contain each of the band's albums).
Edit: As I was finishing up this post, I tried the "add folders" option again, but this time, just for the hell of it, I tried selecting "recursive scan" in the "add folders" window, and that loaded up all the music files in the subfolders and even started playing them. So, not really sure what's going on...