The Restart button emulates a power cycle by randomizing memory.
Disk reads seem to work. Select a .nib or .dsk image, hit reset, type PR#6. It seems slow and there's no activity indication so be patient.
One quirk (feature): if there is no .NIB file loaded, the disk II PROM won't show up in memory where it usually does. This is so it acts like an Apple without a disk controller card when no disk image is present.