Filter which calendars you see
One popover, with search, per-account all or none, and a colour per calendar. A small feature with a large effect on a busy week.
The header tells you how many calendars you are currently showing out of how many are available — "3 of 7 calendars" — which is a quietly useful reminder that you are looking at a filtered view rather than everything.
The important distinction, and the one that catches people: hiding a calendar changes what you see, which is not necessarily the same as what blocks a booking. If you rely on availability, check your booking link rather than assuming the two match.

Steps
Open the sources popover from the header
It shows how many of your calendars are currently displayed out of how many you have connected — "3 of 7" — which is a quiet reminder that you are looking at a filtered view.
Most people have more calendars than they realise, because shared and resource calendars arrive without anybody adding them.

Use search when there are many
Organisations accumulate shared calendars quickly, and scrolling a list of twenty is slower than typing three letters.
Use per-account all or none
Faster than ticking fifteen boxes when you only want one account's calendars.
Set a colour per calendar
Work in one colour, personal in another, team events in a third. This is what makes week view readable at a glance rather than a wall of blocks.
Remember hiding is not excluding
What you display and what blocks a booking are separate questions. If you have hidden something to reduce clutter, confirm your booking link still behaves as you expect.
Check it worked
Hide a calendar, then open your booking link and check whether the slots changed. That single test tells you how display and availability relate in your setup.
The parts people get wrong
- If you are seeing rooms, resources or colleagues' shared calendars, hide them. They rarely say anything about your own day.
- Colours are per calendar rather than per event, so the scheme is worth setting once properly.