NB: This no longer works in macOS Mojave (Apple have ‘deprecated’ the feature.)
Their replacement approach doesn’t allow the same functionality - sorry!
iThoughtsX has a complementary Safari Extension. This is a button in the Safari toolbar which, when clicked, will send the current page title, URL and any selected text over into iThoughtsX - where it will be turned into a topic.
NB: Requires iThoughtsX v2.29 or later.
There are 2 config options that can be administered in the Safari Preferences window - as follows:
The Target map path is the full path to the map into which the topic will be inserted. Best way to administer this is to drag/drop the target ITMZ file from Finder into the text box (this will insert the path automatically.) If this field is empty then the topic will be inserted into the currently open map.
The Target topic is the topic under which the new topic will be inserted. The text in this field will be used to locate a topic in the map (i.e. the text must match a topic's text.) It can even be a regular expression. If this field is empty then the topic will be inserted below the currently selected topic. If no (single) topic is selected then it will be inserted below the root topic.
Click me to download the extension (on OS X)
(then double click the .safariextz file in your downloads folder)
(you will need to restart Safari)