When you are trying to include a text as an effect in a trigger there is a deployable list of "resources". On the other hand, if you try to include a resource, what you get is an ampty list.
There is no possibility to include a text: they are not swapped.
Get into the editor.
Place a trigger and go into effects.
Change type into text or resources.
Screenshot is in Spanish, but the issue appears also in English. It is not a localization problem.
For the time, you can use scripting commands to achieve the same text effect. The command is setTitleEffect.
Syntax: TriggerName setTitleEffect [Type,Effect,Text]
Example: AlertTrigger setTitleEffect ["TEXT", "PLAIN", "Hostiles inbound to this location!"];