Missing documentation for advanced search syntax

[michaelk83]

The advanced search (#1797) syntax is documented inside KPXC, but I could not find it in the main docs (User Guide).

[droidmonkey]

https://keepassxc.org/docs/KeePassXC_UserGuide.html#_searching_the_database

[michaelk83]

My bad, I was looking at the Getting Started guide.