I recall I have had issues with single step and variables. I think one issue I had was setting a global variable. I cannot remember if setting the global on layout enter fixed the issue or if I just moved it to a script. I saw the problem as intermittent, but maybe it was only on first use. Single step has been a little unreliable for me in some cases.
use $$path instead of $path so that you can see it in data viewer.
One report of an issue like this = User probably not doing something right.
Two or more reports of the same issue = report as bug.
Single step buttons should work every time without fail.
I've seen similar problems with variables. It seems like sometimes FileMaker does not recognize the variable without a little help. Try using a multi-step script. Get rid of the Let statement and use a Set Variable step instead to set the path. If that still doesn't work, add a Refresh Window step after the Set variable step.
Thanks for replies.
"Export and open" is exactly simple task, but there is an only place to set variable so I tried using repetition calc.
I tested changeing UUID to CurrentTimestamp, then it is clear that the $path is stored until next time the button is clicked!
This variable can be referred from only in the button.
I don't expect the single step work as "expected", since there is no definition which parameter is evaluated first on target field repetition and export path, but remaining $variable may be bug...
If this is not a bug, there may be something interesting use.