Can't use trial version as a Photos Extension?

[Tillie]

Hi

Is it possible to use the trial version of Pixelmator Pro as a Photos extension? This is the primary workflow I'm interested in and I have not been able to configure this so far. Pixelmator Pro does not appear as an option in the System preferences.

Thanks

[Tillie]

Finally figured it out: Pixelmator Pro is available from the Edit menu, but not via Extensions.