I am running palapeli under mate. I have put preferences in caja (the file explorer in mate 1.20.0) to show hidden files and folders. But if I try to create a new puzzle using caja, it doesn't show me the hidden files and folders. In caja itself, it shows the hidden files and folders itself. I dunno whether it's an issue in caja or palapeli. I'm sharing attachments of the whole thing, maybe somebody can better understand it better than me.
Created attachment 112655 [details] the browse feature to find picture to create puzzle from.
Created attachment 112656 [details] partial view of caja in mate desktop via palapeli
As can be seen, no hidden directories can't be seen.
As mentioned in my reply to your report https://bugs.kde.org/show_bug.cgi?id=394256, re EXIF, Palapeli uses a KDE or Qt library file-dialog to find an image file, as do other apps based on KDE or Qt. I do not know what caja and mate are, but they are not supported in Palapeli, nor is any other specific file manager or desktop. The idea is to have portability of the app across operating systems and desktops. The image Palapeli is looking for should not be in a hidden file or directory. The puzzles it creates are in a special file format and are stored in a special directory in your user-area. You can find and view these files from your desktop and command-line or file manager, but editing them may destroy your puzzle.