Re: Cold foldingJMP is buggy and code folding has always been problematic. Save and re-open the file is one way to fix. Try auto-formatting as well.
Re: Cold foldingThis is how my jmpKeywords.jsl looks like

{"If", "For", "For Each Row", "While", "Try", "New Window", "Function", "Panel Box",
"New Namespace", "New Table", "Define Class"}
Located in C:\Users\\AppData\Roaming\SAS\JMP

And as @ErraticAttack mentioned Script Editor's code folding can be fairly problematic, usually code reformatting helps but sometimes you will have to re-open (and maybe then reformat) the code.
Re: Cold foldingthanks @ErraticAttack and @jthi for the quick reply, simply re-opening does the trick indeed
Code foldingRunning JMP17.
I've been looking into code folding but it does not seem to work as expected. When I use the Expr() function I see the section collapse with the icon to expand. When I use Try() however the code is collapsed but there's no way to expand it again. Am I not understanding something? Also, below link speaks of a custom list that can be defined in jmpKeywords.jsl, but it would be nice to see an actual example of that.
https://www.jmp.com/support/help/en/15.1/#page/jmp/add-code-folding-markers.shtml#
Expr()

Try() -> no expansion possible, also not through right mouse click - > expand all

My settings

Mass CustomizationRe: Code foldingGreetings - i want to let folks know that this issue was reported to JMP Support and this particular issue with code folding is expected to be resolved in the next major version of JMP (JMP 18).