A layout per screen

One dashboard looks right on every screen, and the sidebar lists your dashboards the way you want them.

The sidebar shows the dashboards you chose, in your order, and is saved to your account, so every browser shows the same one. A new dashboard always shows there; hide it if you like. The switcher (⌘K, or Ctrl K) finds every dashboard, shown or not. Tidy your sidebar shows groups, hiding and the right-click menu step by step.

Edit sidebar is the pencil beside +, and is also in the menu under your name and in the switcher. Done or Escape saves it.
A group’s menu changes its name and icon, hides it, or deletes it; its dashboards stay.
Reset brings back the pages a new account has; your dashboards and groups stay as they are.
Each browser remembers which groups are open.
While editing, the house beside a dashboard makes the app open on it when you start it, instead of on Devices; press it again to stop. The dashboard shows Opens on start above its name.
A dashboard’s right-click menu in the sidebar hides it too, and ⇧↵ shows or hides it in the switcher.

One dashboard, three layouts

A dashboard arranged for a laptop is cramped on a portrait tablet and a long column on a phone. So each dashboard keeps three arrangements: Phone, Tablet and Desktop.

Tiles, their settings, styles and taps are the same on every size. Only where tiles go, and which are hidden, differs per size.

A window under 720 px wide shows Phone, 720 to 1099 px shows Tablet, and 1100 px and wider shows Desktop.
Desktop is the main arrangement. A size you have not arranged follows Desktop, so a move on Desktop shows there too.
A phone that follows Desktop shows the tiles in reading order. Most go across the phone; small ones share a row: a tile one column wide takes a quarter of the phone, and one two or three columns wide and at most two rows tall takes half.
In edit mode, the size switch says for each size whether it is Arranged, Follows Desktop or the Main layout, and counts tiles waiting for a place.
Follow Desktop again throws a size’s own arrangement away, after asking.
Adding a tile puts it on every size, in the same section. It carries a New here tag until you place it or choose Keep it here.

You edit from a wide window. On a phone itself, Edit dashboard in the menu says it needs a wider window. Arrange tiles for each screen size shows arranging Phone and hiding a tile there step by step.