Use the Combine Face Groups tool to combine face groups on a mesh body in Fusion.

In the Design workspace, on the Mesh tab, select Prepare > Combine Face Groups
.
The Combine Face Groups dialog displays.
In the canvas, select two or more adjacent face groups on a mesh body.
Click OK.
The combined face groups display on the mesh body in the canvas. A Combine Face Groups feature displays in the Timeline.
Shift+F to display Mesh Face Groups on mesh bodies.