In addition to a checkbox in the Drafting Settings dialog, an icon on the status bar, and a 3-letter keyboard shortcut, each Object Snap has its own unique numeric identifier.
- 0 - NONe
- 1 - ENDpoint
- 2 - MIDpoint
- 4 - CENter
- 8 - NODe
- 16 - QUAdrant
- 32 - INTersection
- 64 - INSertion
- 128 - PERpendicular
- 256 - TANgent
- 512 - NEArest
- 1024 - Clears all object snaps
- 2048 - APParent Intersection
- 4096 - EXTension
- 8192 - PARallel
- 16383 - All object snaps
When you turn on a running object snap, it gets added to the value of the OSMODE system variable. For example, if you had only Endpoints and Centers turned on, OSMODE would be 5. The way that the values are defined means that every possible combination yields a unique sum.
According to Help, the default is 4133, which corresponds to End, Center, Intersection, and Extension. Once you get your own preferred snaps, you can check the value of OSMODE and save it for future reference. You could just remember it, or you could assign different values to buttons on the ribbon to activate different combinations for different tasks.
My favorite OSMODE is 4223 -- what's yours?

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