The easiest way I think would be to open your embedded object (CTRL+SHIFT+O).
Then "Save As" with a new name.
It will still be in your embedded library.
Now delete the original (in Library manager) - but if you have already placed some instances you will want to select them first (one at a time because they probably have different lengths and/or heights), then go into the object settings and find the new gutter object.
But before you click it to swap it, hold CTRL+ALT (i.e. the syringe) and then click on the new object and all your original settings will be passed over to it.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11