It is - in our opinion - not a good idea to merge all glossaries in a single big glossary. When used in the booth, the tool needs to be quick and present you only relevant results. However, we do acknowledge the need to search the whole database (all glossaries) when no results is produced inside the assignment glossary (or the assignment glossary + some other relevant glossary manually selected by the interpreter). For this reason, we developed a search algorithm that will search in ALL your glossaries IF no relevant result is found in your selected glossary. This function is found in the Search settings (you can open it from the conference modality) under the name "Progressive search". In this way the search algorithm will be quick and will extend its search to all your glossaries, if this is needed. In some respect, it imitates the "search all" option you suggested.