Since FileZilla inherits its look from the OS, you must change your system-wide settings:
Choose a different icon set (e.g., Breeze , OpenCritic , or Tango ) to change the toolbar's visual style. Workarounds for Windows Users filezilla dark theme upd
Since the official method is fragile, advanced users use a manual patch. This method replaces the internal theming resources. Since FileZilla inherits its look from the OS,