With SMA (Slot Mid-Axis), you can create a Middle Work Axis for Slots in just one click.
The created Axis will remain in the middle of the slot, and changing slot parameters won’t affect the created Axis.
It will always point to the middle of the slot, making it a convenient solution for centering holes from one plate to the middle of a slot on another plate in Autodesk® Inventor®.

How it works 

SMA (Slot Mid-Axis) can be started from both Assembly and Part Documents, allowing users to create a Middle Work Axis for their Slot in just one click regardless of the document type they are working on.
Overview: https://youtu.be/A0OT92wBaE4

1. The App will ask you to select one of the Slot faces.
2. It will analyze your selection.
3. Check the best way to create the Mid Axis.
4. Creates the Mid Axis.
5. Renames the Axis to its Feature.
6. Rearrange your Browser.

The Add-in has worked for Inventor releases since 2020.

The installer that ran when you downloaded this app/plug-in will start installing the app/plug-in. OR double-click the downloaded installer to install the app/plugin.

You can unload the plugin without uninstalling it by unchecking the “Loaded/Unloaded” checkbox associated with the plugin in the Inventor Add-In Manager. You may have to restart Inventor to unload the application completely.

To uninstall this plug-in, exit the Add-in if you are currently running it, simply rerun the installer, and select the “Uninstall” button. OR you can uninstall it from ‘Control Panel/Programs and Features’ (Windows 7/10/11), just as you would uninstall any other application from your system.