Equals supports the full set of Excel alt mode shortcuts. On a Mac, use option to enter alt mode. On a PC, use shift-alt to enter alt mode.

Once you enter alt mode you will see the toolbar light up:

You can then follow the hints to systematically trigger any action in the spreadsheet. For example, press H to access any of the actions in the blue area above:

Now you see the hints for the actions within H. From here, if you press 1 it will toggle bold on the selected cell.