Okay.

  1. Click the a PushButtonMorph 1 [192@183 | 25@25] button. It appears in the block palette.
  2. Create your block in this menu. (I made a custom category, but you don't need to.) a BlockDialogMorph 7 [539@173 | 288@341]
  3. Press a PushButtonMorph 1 [616@470 | 49@31].
  4. in the block editor, click the + at the end of the name of the block. image|110x64
  5. You should see a menu like this: a InputSlotDialogMorph 6 [429@151 | 278@165]
  6. Click a ToggleElementMorph 0 [548@230 | 100@27], then click the little arrow.
  7. You should see a InputSlotDialogMorph 6 [429@151 | 508@387]
  8. Type a name, like "Menu".
  9. Click the a PushButtonMorph 1 [882@438 | 25@25], then click a MenuItemMorph 1 [897@450 | 82@14].
  10. In the box that pops up, type in the options you want, one line per item: a DialogBoxMorph 4 [469@217 | 428@255]
  11. Press OK on all the dialogs.

If all goes well, you should have your block!