Alert composer expression to display text only in email and not bell notification

Summary:

We have requirement to display some text in the message in alert only in email and not in bell notification. We had used the option for isonline variable in BIP template. The same needs to be implemented using alert composer now. Please suggest the expression which can be used conditionally to achieve this.

Content (please ensure you mask any confidential information):

We have requirement to display some text in the message in alert only in email and not in bell notification. We had used the option for isonline variable in BIP template. The same needs to be implemented using alert composer now. Please suggest the expression which can be used conditionally to achieve this.