Correct.
There are two sources of engine vibration making its way into the cabin. One is a failed mount (engine or transmission) and can be hard to spot externally. The other is something attached to the engine making contact with something on the car. This can be something detached from either.
The only other source isn't direct but something vibrating in sympathy (probably not mounted as intended) eg, my warning triangle. Usually, it will only occur at certain (not all) engine rpm.
You just have to work through the list until the culprit is found.
edit PS.
There's an outside possibility of vibration being transmitted through the controls. Unlikely to be throttle as likely an electrical connection only, but clutch cable (if manual) and possibly gear linkage. But either should be felt through the pedal or lever.
Yes that’s what we’re looking for think it’s something touching the engine or gear box just taking a long time finding the issue !