Looking up the official website, I see a more recent version there (1.3). Adding the PPA and installing
handbrake-gtk I get 1.2.1 version (because my system in ubuntu-18.04-based, newer versions of Ubuntu should get even newer versions): this has a different interface, one with a button that was absent in the other version.
Also, the preset is automatically loaded after bring imported.
Testing again with
handbrake old 1.1 (which removes the newer version) it gives upon startup a warning that presets newer than the present version of Handbrake are present.