Online Obsidian Help is hosted as an Obsidian Publish site. The ability to search note contents on Obsidian Publish sites is an outstanding feature request Publish - seach content of files and tags
The help vault Obsidian included in the desktop app used to have the same content as the online help, just in a local sandbox. You could full text search in that.
As of 0.14.3, the help vault has been replaced with a stripped down help vault that doesn’t include everything that’s in the online help. For example, that search help page in your screen grab no longer exists.
If you are not on an insider build, you should still have the full help vault I think, so you could open that and do a full text search.
@WhiteNoise do you think we could bring back the full help vault? For cases like this and offline use, having the full help vault local is still useful.
I use the online help as it is more up to date. For example, I am currently running v0.14.2 and the local help vault doesn’t have a section about callouts.
One of the things we are encouraged to do as users is to search the help resources. Feels counterproductive for the online help not to be fully searchable, but it is what it is.
I can use Google’s site-specific search tool as it works to search content and headings. For example, boolean site:https://help.obsidian.md yields this. Joy!