I tried to use the {popup:short text:long text}; it highlights correctly the short text, but when I click on it nothing appears. I thought it was because of a nested command in the long text, so I deleted this nested command, but to no avail.

Can you post the whole text you used?

It's in Italian.
Here it is:
{popup:simbolo strano:sembra una persona segata in due da una sbarra diagonale, col corpo posato su una delle estremità e le gambe appese all'altra.}
I tried to remove apostrophes and letters with accents but it didn't work.

It is because the short text is two words. I had not realised, but it will only work if that is just alphanumerics. I will get it sorted for 5.7.2, but that is a couple of months away, so maybe not much help.

Thanks. My game is far from being ready, so I think this popup can wait for 5.7.2.

I had that issue too. I was able to display the two words and make the popup work for one of them, just not for both words at the same time. I made an incomplete popup for the first word (without the long text string), and a fully functioning popup for the second word, placing them side-by-side.

{popup:blue :}{popup:gem:COOL!{img:blue-gem.jpg}}

Clicking on "blue" would do nothing, but clicking on "gem" would show text and a pic.