There are several places where a hotkey can be set for this.

In Keymaps > General it is set to Shift-Alt-F. When I try that the toon casts the spell bound to the F key.

In Keymaps > Non-combat I set up a hotkey. It turns follow on but not off.

In Keymaps > WoW Non-combat I set up a hotkey. It produces messages that say follow is being toggled and Jamba reports follow has broken. But the minions still follow.

How can I toggle follow?