The modlist.txt controls which mods are being loaded and the order they are loaded.
To change the order, you would edit the order the mods are written in the modlist.txt using the Text Editor in the Configuration File option in the server's control panel.
Mods are loaded in the order they are written in the file.
The first mod written in the file is loaded first, the second mod in the file is loaded second, and so on.
Example modlist.txt
In this above example, Savage Wilds is the first mod to be loaded, Pippi is the second mod to be loaded, and Emberlight is the 3rd mod to be loaded.