I am converting from 123 and have always placed macro buttons where they
would be in view at the appropriate place in the spreadsheet.

From the top menu, click View Toolbars Forms. When the box appears,
click the 4th box in the top row ("Button"), position the cursor on the
spreadsheet, and left-click while you drag the cursor to indicate the
size of the button (this can be adjusted later). Then a window should
appear that prompts you to assign a macro to that button.