Where are the quick launch entries of the top bar saved in Ubuntu 18.04 Mate 32-bit?

I am running Ubuntu 18.04 Mate 32-bit. Sometimes when I add a program shortcut to the quick launch section of the top bar, it will be gone after a restart. I hope to bypass that by manually editing the respective configuration file. I am rather new to Linux and do not want to simply edit some file by my own choice. So can you tell me which is the correct file to edit?

They are stored in dconf database. In the corresponding /org/mate/panel/ "folder".

Way to backup is

dconf dump /org/mate/panel/ > ~/dconf_panel

Way to restore use

dconf load /org/mate/panel/ < ~/dconf_panel

Note: each panel object is contained in some hierarchy, so it is difficult to extract every single object.