This works for me: Enabling Transparency (#99) · Issues · Christian Hergert / ptyxis · GitLab
This sets transparency in Ptyxis with the currently-used profile (run in ptyxis):
gsettings set 'org.gnome.Ptyxis.Profile:/org/gnome/Ptyxis/Profiles/'$PTYXIS_PROFILE'/' 'opacity' '0.95'
On that comment page, there’s these commands to get the default-profile-uuid UUID:
gsettings get org.gnome.Ptyxis default-profile-uuid
And to set it with that default-profile-uuid:
gsettings set org.gnome.Ptyxis.Profile:/org/gnome/Ptyxis/Profiles/${ID_VALUE_FROM_ABOVE}/ opacity 0.8
The uuid could probably be changed to different Ptyxis profiles too and obtained through the Ptyxis Profile settings → Copy the UUID or obtained from gsettings.
There’s notes on that issue about why it isn’t exposed yet implying potential issues, but seems fine for me after a few mins 