Hi Tim,
Thanks for your detailed explanations, which have been most useful.
2. That's exactly what I thought I should do, but did not know how. I did not know you could use parent:: that way.
Thanks for the tip to use record_exists.
3. "Conversely, the other methods mentioned are designed to be extension points to let you safely change all the things you might reasonably want to change." Yes, but my point was that I do not know where to find, e.g. get_edit_controls() function.
You did not answer my question : What does {@link} mean in moodle comments?
4.- Point taken as regards (b). By the way, is it at all possible to not display the (b) settings, which, in the case of my block are useless?
Finally, I agree that the most reasonable thing for me to do is to leave the Edit icon in place and put my test for the existence of glossaries in my block's edit_form.php. That way I won't "break" anything.
Joseph