Theme list goes blank after drag and drop installation
Tested on Xubuntu 19.10 (settings-manager 4.14.1), Xubuntu 20.04 (settings-manager 4.14.3) and xfce-test built on August 1st (settings-manager 4.15.1-39-g1d0c21be)
After installing a new theme with drag and drop onto the Appearances dialog, the list goes blank and you have to restart Appearances to then apply the theme.
Test theme - https://github.com/dracula/gtk/releases/download/v1.3.0/Ant-Dracula.tar