You can sort macros by Date Used to find macros that have not been used for a long time.
Most interestingly perhaps, you can sort macros by Size. Since macros are generally very small unless they contain images, you might find that your macro file size is largely dominated by just a few macros. Deleting them or moving the images out of the macros might be the answer.
Otherwise, you can export macros and delete them and re-import them later if necessary. You can use the Export All Macros as a Folder and then just delete the ones you aren't using.