Please note that there are two ways of writing expressions. Which mode is being used is set by the application.
On the one hand, there is the normal expression mode, in which you can enter names of variables and functions without brackets. Fixed text must be enclosed in quotation marks. The individual variables must be joined with the "+" operator.
On the other hand, there is the extended mode, in which you can enter fixed text without quotation marks. You must enclose variables with "<" and ">" and functions with chevrons ("«" and "»").
In this mode, you can insert the chevrons by clicking the "Insert chevrons" button (e.g. if you want to enter a function directly". You can also use Alt+174/175. It is not necessary to use an operator to join individual operators in this mode. The extended mode is easier to use.