I would like to create a page in Joomla without showing it in a menu. That would be easy when the URL could be from the root, e.g. www.mysite.com/hiddenpage I would just make a menu without module to show it and assign a menulink to that hidden menu.
However the url should be www.mysite.com/parentpage/hiddenpage So the page should be linked to another existing page as a childpage but without showing in the menu.
So far this seems not possible? Am I overlooking a feature in Joomla which would allow me to simply deactivate visibility in the menu without preventing the page from being accessed from the internet?
Or perhaps is it possible to edit or override a core component to force Joomla to allow this behaviour?
UPDATE: Too much thinking in one direction... The solution to do this is to edit the menu-item > linktype > css give it class "hide" (integrated bootstrap class) to just block visibility in the menu...
No this is not possible with Joomla.
There are several options for you to achieve the same result, I list them in order of ease.
Use joomla redirect component. Simply tell the user to surf to the url he wants, he will then find it in the administrator - components - redirect, where she can insert the non-sef url.
Tell them to use a different prefix: i.e. create a hidden menu where they will add the direct links;
Additionally, in order to remove the id from the url you can:
Install simplecustomrouter extension, it should do the job out of the box but some coding may be required on your part in order for it to work properly; extremely lightweight.
Go for a blasoned SEF extension such as sh440sef, this will add some overhead and may require a lot of work in configuration.