In 2.79 and earlier, we had a panel inside the sidebar called 'Item'. In here you could rename objects inside the viewport:
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Riggers liked to have a fast way to rename things directly in the viewport.
We removed it because it was quite arbitrary and out of place. But when we did that, we thought to add a popup operator to replace it, like so:
{F6592818}
This is similar to the M-key popup for Collections.
We just never got around to adding this. Therefore, this task is here so we don't forget.