So, it means this variable has to be a user-readable name, not any variable name that i prefer in my script. So, i cannot ask the user: Fill in your name here: and the date given will be stored in variable "username".
Yes, there is a trick for this. Select Help from the gear menu in the action to take you to the wiki, which lets you have a unique name for a variable without showing the whole details (eg MyVariables__Show This).
The variable will still be the full long name, if you want to change it for simpler use in a script, you will need to copy the long display name to a shorter name, eg:
Set Variable “ScriptVar” to text “%Variable%Marker 1 name%”