In 4.3, we removed the ability to manually configure an External Tool instance. I.e. users cannot add an "External tool" instance from the activity chooser any more. They instead, must configure a site or course tool, and then use that tool to create resource links (using content selection, most likely).

This workflow is ok, provided the tool supports content item selection (deep linking). Which of course, is not the case for all tools, particularly the old 1.1 tools (in LTI 1.3/LTI Advantage, deep linking is part of the core suite of specs so most tools implement it in order to be certified).

We're seeing reports of tools which are using URL params to identify resources (e.g. tool.example.com?resource=123 or even the old Moodle provider code). https://moodle.org/mod/forum/discuss.php?d=454439.

Previously, the URL param would be entered in the instance form (in the tool URL field), and the tool could load that specific resource on launch. Teachers could paste in the URL, including the params, and it would launch that specific resource. This was a means of sharing access to the specific resource without deep linking too.

Now, since we've nowhere to set that in the instance form, and more specifically no way to indicate a resource id at all (it's all hidden and tied into deep linking workflows), the only way tools like this (those which don't support deep linking) can create links is to create one tool PER RESOURCE, in the course tools page. This, of course, is hugely clunky and not practical at all.

This issue is not about re-adding the URL param support - we don't want to do that. Instead, it's about considering whether we want to surface the 'custom params' form field again, under an 'advanced fields' section of the form, so that teachers can enter the id of the resource - should the tool support loading the resource via custom params. This won't instantly solve the problem for tools like the above, which use URL params, but it does at least provide a proper avenue to set resource ids and the like, should the tool not support deep linking.

References:
MDL-78573 is the 4.3 Epic, but the form was locked for legacy tool instances in MDL-78597.
https://moodle.org/mod/forum/discuss.php?d=450974#p1813411
https://moodle.org/mod/forum/discuss.php?d=454439