To change the slug and the URL structure for your glossary and for all related archives, follow this procedure.
In the plugins’ settings panel, change the default value (glossary) with your desired name in the “Glossary terms slug” field. This will change the default “yoursite.com/glossary” slug in “yoursite.com/yourslug”
In the same panel, right below, you can also change the behavior of the slugs of the glossaries’ categories. Here too you can change from the default “yoursite.com/glossary-cat“ into “yoursite.com/yourslug“ making sure it differs from the previous/above one.
Remember: slugs may not be equal nor can they correspond to a pre-existing slug in use (i.e., a slug already used for a page or for a category published on your website).
You might need to flush or update, the permalinks once you have set this option.
To flush permalinks, head to the WordPress dashboard and select “Permalinks.” Once on that page, just save the current settings, and automatically WordPress will refresh them appropriately.