LM1086ILD-3.3/NOPB Operation

The center pad is the substrate of the die. The other Vout pads may have sense leads bonded to them. The data sheet does not have any info on it, but it is always advisable to tie all pins together of the same type.

I have seen more than a few chip specs that state that some ground points are for heat sink attachments, while others are tied to the ground circuit's current paths.

In some cases multiple ground points are designed specifically to tie together external to the chip. There may be a small conduction path or leakage from multiple ground pins, but a better conductive path is usually needed for correct operation.

My general rule-of-thumb concerning ground connections: All or nothing. Do not even bother to try to run a chip without all grounds tied together in some way unless you have a specific strategy that requires splitting them up.