Here's another approach. This has worked very well for me for many years. It is simply a matter of creating a few very simple lisp "macros". See the attached .gif. This is most effective if you store your macros in a file that is part of the Startup Suite, via the APPLOAD command. Referring to the attached .gif, with the example file loaded, you only need to enter "4" at the command line and center snap will be active. Likewise, "2" is midpoint snap, "16" is quadrant & "5" is a combination of end & center. Look at your Osnap dialogue, pick a few options, then, after exiting, type OSMODE and you will see a number corresponding to the osnaps chosen. In this way you can further customize your .lisp file the way you like it.
LC