Shift + I in Maya default keys isolates a selection, but has no hotkey assigned to bring it back. The reason, I believe, is that people prefer to make isolations within their prior isolations, instead of having it toggle. I personally prefer the latter, using it a lot to temporarily hide things as I work on a specific area. Going to the current panel’s Show > Isolate Select > View Selected was a little too tedious for me, so I mapped this script to a key.
//Toggle Isolate Selected in Current Panel
$currentPanel = `getPanel -withFocus`;
$state = `isolateSelect -q -state $currentPanel`;
if ($state == "0")
enableIsolateSelect $currentPanel 1;
enableIsolateSelect $currentPanel 0;
For those who have no idea how to map it to a key: