And similarly:
#!/bin/bash
varName="someTempVar"
varValue="some temp val like 42"
osascript -l JavaScript -e "function run(argv) \
{Application('Keyboard Maestro Engine') \
.setvariable('$varName', {to:'$varValue'})}"
for:

or perhaps more flexibly:
#!/bin/bash
# Two quoted arguments: KMVarName KMVarValue
setKMVar() {
osascript -l JavaScript -e "function run(argv) \
{Application('Keyboard Maestro Engine') \
.setvariable('$1', {to:'$2'})}"
}
setKMVar "someName" "some string value"
