CanLII Offers Multi-Database Search
According to a recent CanLII blog post:
"Upon clicking on each jurisdiction on the screen, a panel will open smoothly and it will offer you a list of all available databases for that particular jurisdiction. From that list, you will be able to select the databases that you wish to search."
"By default, no databases are selected, so you have to choose at least one before you launch your search."
"A counter indicates how many databases you have selected in every jurisdiction. You can also use shortcuts to select all databases at once."