Okay, I played around with Keywords ToolTip Generator (KTG) a bit, and think I have a few options for you. None of them require changes to Insert Pages, which I think is functioning as it should.
First, the problem seems to be how KTG hooks into the_content filter. Each inserted page also gets filtered through the_content, and somehow this is preventing KTG from executing its the_content filter.
First option:
index.php line 152 is where KTG hooks into the_content. If you change their priority to 11 (instead of 100000), it should work. You may want to open an issue with the maintainer of that plugin, because it’s inadvisable to just hack plugin files (any updates they release will overwrite your change).
Second option:
You can disable the_content filter on inserted pages, which would avoid the conflict with KTG. Keep in mind that this means that the content of all inserted pages won’t get the filter applied, so if you have shortcodes or other content that gets filtered, it won’t get parsed.
You can do this by adding a filter to tell insert pages to disable the content filter. Put the following add_filter() call in your theme’s functions.php within the init action, like so:
function theme_init() {
// Disable the_content filter for inserted pages.
add_filter( 'insert_pages_apply_the_content_filter', function ( $should_apply ) { return false; } );
}
add_action( 'init', 'theme_init' );
Third option:
In the past I’ve used the Explanatory Dictionary plugin alongside Insert Pages without any problems.
https://www.ads-software.com/plugins/explanatory-dictionary/