I've not done it with Joplin, but I have "moved" other apps that seemingly have no way of installing them selves on other drives.
I moved the program directory and the data directory to the drive I wanted to use, then created Symbolic Links back to their original locations.
One BIG caveat is that depending on HOW the app does updates, it may wipe out the sym links when updating and create the app and data folder back on the C: drive.