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The syntax for the built-in remapping feature is OriginKey::DestinationKey. For example, a script consisting only of the following line would make the A key behave like the B key:

a::b
S↓
The above example does not alter the B key itself. The B key would continue to send the "b" keystroke unless you remap it to something else as shown in the following example:

a::b
b::a
S↓
The examples above use lowercase, which is recommended for most purposes because it also remaps the corresponding uppercase letters (that is, it will send uppercase when CapsLock is "on" or the Shift key is held down). By contrast, specifying an uppercase letter on the right side forces uppercase. For example, the following line would produce an uppercase B when you type either "a" or "A" (as long as CapsLock is off):

a::B
S↓
However, a remapping opposite to the one above would not work as one might expect, as a remapping never "releases" the modifier keys which are used to trigger it. For example, A::b is typically equivalent to A::B and ^a::b is equivalent to ^a::^b. This is because each remapping internally uses {Blind} to allow the key or key combination to be combined with other modifiers.

remapping