I'm not even sure how you ever got that to work. I've never heard of that before.
Of course, the Fill Down command is available as a menu item, but I've always found it most convenient to assign the
Command+D keystroke command to it. It actually
was one of the default keystroke commands in older versions of Excel, but I think they changed it to
Control+D in the first version of Excel for OS X.
Anyhow, you can set the Fill Down command to work with any keystroke combination you want in the Customize Toolbars and Menus dialog:
Under the View menu, select
Toolbars, and then choose Customize Toolbars and Menus... from the submenu to open the Customize Toolbars and Menus dialog.
Click on the Keyboard... button at the bottom right edge of the dialog to open the
Customize Keyboard dialog.
Select the Edit category on the left, and then scroll down the list of Edit commands on the right and select the
Place the cursor in the Press new shortcut key text box, and type whatever keystroke combination you want to use.
If the keystroke combination is already in use by another command, Excel will tell you that it's currently assigned and will tell you what function it's assigned to. If you want to override the current assignment, click the
Add button. Excel will display a prompt asking you whether you want to reassign the key combination to the selected command. If so, click
OK, or click
Cancel to return to the dialog and select another key combination.
When you're done, click OK on both dialogs to close them.
Sorry that I can't tell you how to make the double-click work. I guess there might be a way to write a macro using mouse actions for something like that, but as far as I know, there's no way to assign mouse actions to Edit functions in the normal user-definable
interface features in Excel.