Hello Andrea,
To make “Custom session window” disappear from nx webplayer, please run following commands:
/etc/NX/nxserver –ruleadd –class session –type unix-console –value no
/etc/NX/nxserver –ruleadd –class session –type unix-default –value no
/etc/NX/nxserver –ruleadd –class session –type unix-application –value no
BR,
NiKO