I was looking for a way to send a direct message and couldn't find it right away. After poking around in the app and looking trough the FAQs I finally found the answer in this issue: https://github.com/tuskyapp/Tusky/issues/1953. I suggest adding this to the FAQs.
Q: How do I send a direct message?
A: Create a toot, mention the user and set the visibility (World icon) to Direct.
I was looking for a way to send a direct message and couldn't find it right away. After poking around in the app and looking trough the FAQs I finally found the answer in this issue: https://github.com/tuskyapp/Tusky/issues/1953. I suggest adding this to the FAQs.
Q: How do I send a direct message?
A: Create a toot, mention the user and set the visibility (World icon) to Direct.