zotLook 1.2.3
The windowed contact sheet moves to Ctrl+Alt+Space
Ctrl+Shift+Space shows the contact sheet in the system's preview panel; Ctrl+Alt+Space now shows it in a Zotero window. The same work in a different frame, one modifier apart — where the previous default, Ctrl+Shift+Tab, said nothing about what it does.
Checked on all three systems rather than assumed. Microsoft's own list of Windows shortcuts claims Alt+Space (window menu), Ctrl+Space (Chinese IME) and Win+Space with Win+Shift+Space (input languages) — and not Ctrl+Alt+Space. That list is also why the Windows key is no candidate: Win+Space is spoken for, and Win combinations rarely reach an application at all. GNOME takes Alt+Space and usually Super+Space, not this one. Zotero binds no key to the space bar and keeps its own configurable shortcuts on single letters.
::: One caveat, stated rather than left to be discovered
macOS lists Ctrl+Option+Space as previous input source — switched off where a machine has one input source, and on where it has several. On such a Mac the default is swallowed and nothing happens; Settings → zotLook → Shortcuts is where that gets put right.
:::
Your own choice is unaffected: this is the default, and Restore defaults is what writes it.
Install
Download zotlook-1.2.3.xpi below, then in Zotero: Tools → Add-ons → gear icon → Install Add-on From File… Installed copies update themselves.