As reported in the discussion Changing glossary appearance causes settings cog to disappear sometimes the glossary 'Actions menu' icon disappears.

I investigated using https://school.demo.moodle.net/mod/glossary/view.php?id=650 (log in as a teacher) and reproduced the problem as follows:

1. View a glossary. You should see the 'Actions menu' icon (gear/cog) on the right of the page.
2. Try browsing the glossary by category, alphabet or using the index (clicking any letter).

Expected result:

The 'Actions menu' icon remains visible.

Actual result:

The 'Actions menu' icon disappears. You can only get to the glossary settings again if you know to click on the glossary name link (and so stop browsing by alphabet, category etc.)