How do i travel to the elven capital? At first i thought i had to use an elven character but it seems it wasn't the case, everyone is just red when i attempt to select travelers.

Your might not be in sandbox mode, and i'd guess progression guild quests would be how you do that, or encoutner a npc around town like with the daisy npc.

This appears to be a bug as the Elven Capital was available in past versions. Selecting the Elven capital as a destination generates the following error in the console and/or the log file: 

SCRIPT ERROR: select_destination: Invalid get index 'Elven Capital' (on base: 'Dictionary').
          At: res://GUI_New/Mansion/MansionTravelsModule.gd:91