Yeah, sure.
Just copy & rename the SH3 Folder which is in My Documents. Saved for future use. To re-enable, either copy the contents into the new SH3 folder or overwrite it (My Documents).
What you have to remember though is that if you wish to reuse that save file in the future the basic file set of your SH3 installation must be the same.
For example, you could not save a career from GWX 1.03 and then use it in 1.04 or visa versa.
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