Someone in my office today asked if the Multiple Objects contextual ribbon tab could be suppressed. That is the tab that displays when you select items of different object types.
What remains is the ability to set the maximum number of objects for which a contextual ribbon will display (RIBBONCONTEXTSELLIM System Variable). The allowable range is 0 to 32767, with an initial default value of 2500. The purpose of this is to limit performance issues when trying to act on a large number of objects. When the number of objects selected exceeds the current value of RIBBONCONTEXTSELLIM, then a contextual ribbon tab will not display, and any ribbon property controls will be disabled (grayed out). Setting the value to 0 allows an unlimited number of objects to be selected and still get a contextual ribbon tab, so this cannot be used to turn off contextual ribbon tabs. But setting it to 1 will allow contextual ribbon tabs to display when just one object is selected (which most would find desirable, particularly for AutoCAD® Architecture and AutoCAD® MEP objects), but disable it when more than one object is selected. This effectively suppresses the display of the Multiple Objects contextual ribbon tab, but does also suppress all other contextual ribbon tabs when multiple objects are selected. For example, if you select two or more Walls, the Wall contextual ribbon tab will not display.
In addition to typing RIBBONCONTEXTSELLIM at the command prompt, pressing the ENTER key and then typing 1 and pressing the ENTER key, you can also set this value in the Options dialog, on the Selection tab, in the Ribbon options area by selecting the Contextual Tab States button and then editing the value in the Object selection maximum for contextual tab display edit box.
This value is stored in the User Settings (registry) for a given AutoCAD Profile, so setting it once will apply to all drawings you open.
I personally leave the setting at the default 2500, but if you often select multiple objects of different types with the intent to select a tool on the ribbon that is not on the Multiple Objects ribbon tab and want to avoid having to perform an extra click to get back to where you previously were in the ribbon, then setting RIBBONCONTEXTSELLIM to 1 may improve your workflow.