Hi there,
Do you mean "idle-timeout for any user logged in via SSH"?
If yes then here is the code
set system login class test1 idle-timeout 120
set system login class test1 permissions <permissions>
set system login user test1 full-name TestUser
set system login user test1 class test1
The disadvantage is that this timeout will apply not only to SSH but to telnet and console too.
The alternative solution could be an event-script enforcing a custom idle-timeout for SSH connections.
Rgds
Alex