Vegetable Oil vs. Canola oil in DIY Spreadable butter
In terms of spreadability, the real issue is the level of saturation.

Coconut oil is quite saturated (especially for a vegetable based lipid), and so it is far more solid at room temperature than most oils.   (Cocoa butter would be another exception; it is quite hard at room temperature).

Generic vegetable oil, at least under US labeling laws, may contain any number of vegetable oils including corn, soy, rapeseed (canola) and so on&mdash;or even a mixture of any or all of these.  They are all quite similar in the saturation and viscosity at room temperature, and so any of them should perform similarly in your butter application.

So go ahead and use the vegetable oil.