The View menu has various settings to configure the 3D scene.
Show Wireframe
Turning on Wireframe mode means that we draw all the triangle edges as black lines, for all the Meshes in the scene (below middle). Currently it is not possible to set Wireframe mode per-object. You can also use the w hotkey to toggle wireframe. If you would like thicker wireframe lines, you can add a line "WireframeLineWidth=2" to your meshmixer.ini file, under the Options category.
Left: Boundary edges shown in blue. Center: Wireframe mode is on. Right: Boundaries and wireframe both turned off.
Show Boundaries
By default we render boundary edges of Meshes as Blue lines. You can use this setting to turn off these lines, as shown above-right. Ctrl/Cmd+Shift+b will also toggle boundaries.Show Grid
The ground-plane grid in Meshmixer can be toggled on/off with this menu item. Meshmixer uses a dynamic grid which changes resolution as you zoom in, as shown in the image below. The base dimension of the grid squares is found by clicking to open the Units/Dimension property panel, and reviewing the Grid Size setting.
Showing the grid
Show Printer Bed
When 3D printing with Meshmixer, it can be very helpful to see the printer bed of your printer. Particularly for things like doing support structures of auto-layout. This menu item toggles the printer bed on and off. The printer bed includes a label at the front showing the printer name, and a thin bounding-box visualization of the print volume.
Showing the printer bed
See the Printing topic for more about 3D printing.