It is possible to change the install location of mods with some games, but it requires editing a file to do so. Please note, however, that not all games will respect this setting as some may use a custom implementation.
You will need to find “globalsettings.json” that is located in the …\AppData\Local\mod.io folder. You can also find it by searching for “%localappdata%” in the Windows search bar.
Open the file with a program like Notepad and search for “{“RootLocalStoragePath”:”C:/Users/Public/mod.io/”}“. You can edit this path to whichever folder you would prefer.
Hope this helps!