Hello Valeh,
You may open menus and submenus in new tab by following the steps below
Go to Dashboard >> Appearance >> Menus >> click on “Screen Options” (At Top right) >> Select “Link Target” >> Click on the menus and select “Open link in a new tab” (select this option for all menus which you want to open in new tab) >> Save menu. See in the screenshot https://paste.pics/37fad6c3c4790f8ad873fe08a0fb0455
Thank you.