xfce4-session-4.13.2-2.fc30 Currently xfce4-session-settings opens always with the smallest size possible which is too small to show the list of apps in the auto-start tab. If it saves the window size for the session then we don't need to resize the window always, only the first time. Thank you all for Xfce, I'm conscious these bugs are just suggestions.
https://git.xfce.org/xfce/xfce4-session/diff/settings/xfce4-session-settings.ui?id=73e1213825cc882c932aafb016f8a13f97c17d34 The height was increased by 100px for the next point release. Another goal is to reduce the amount of text above list.
https://gitlab.xfce.org/xfce/xfce4-session/-/commit/59a1a8df4de9ec270f36859fc30d819a607048cf Also, the info text above the list was removed so that there is enough space to show the entries now. Closing this report.