I can confirm that is definitely a locale issue, setting the number format in the way you suggest display correctly the left tab with all entries, here is a snapshot of the User Interface runing this way:

English configuration, dot and comma swapped

The funny thing is that since I never seen along all SDLmame releases the left tab displayed I did not suspect its existence neither I was going to miss something, it was only after your answer I began to suspect an issue and in fact there was. I hope this could be fixed in future release so I can mantain my actual localized settings. Again, many thanks for your support!