Hello,

Only text type in custom field available, but i've planned to add textarea for iCagenda 3.9 (just started development, so stable release by the end of the year if everything go as expected ).

For no, you will have to use "text" type, and you will be able to edit the custom field to textarea when this one will be available.

Other solution, if you don't use the "Notes" core field, you can override it in admin custom fields of iCagenda, and set the name as you want it

Best regards,
Cyril