To display the value of a numeric variable, you can plot it using the plot() function:
plot(variable_name)
This allows you to inspect the variable's value on each chart bar and follow its progression if it changes.
If you want to display the value of a string variable, use the label.new() function:
label.new(bar_index, high, text=syminfo.ticker)
You can also use label.new() to display the value of a numeric variable by first converting it to a string using the tostring() function:
label.new(bar_index, high, text=tostring(high))
The label.new() function will only display the last ~50 values of the variable.