Clicking the "name" of a Calendar Hides/UnChecks all other Calendars?

[Sylow23]

This solution

Clicking aside a calendar deselect all the others

While we consider adding a select-all option, there is an unpublished keyboard shortcut that may offer a solution for you. If you missed hitting a box and ended up unticking all your folders and want them back, click on a folder name so it has a grey background. Click on it again so the background turns blue. Use Ctrl Space which will tick all the folders.

might be a workaround.