Remap non-modifiable keyboard shortcuts in any app
Ever run into a program that has some pre-defined keyboard shortcuts you don't like? In most cases, they're associated with a menu item, which means you can use macOS' built-in keyboard shortcuts function to fix them. (In System Preferences > Keyboard > Shortcuts > App Shortcuts.)
But what if the shortcut isn't associated with any menu item? Such is the case in Excel 365, which replaced a couple easy-to-type shortcuts (⌃I and ⌃K for inserting and deleting rows and columns) with much harder to type versions: ⇧⌃= and ⌃-. If there's no corresponding entry in the app's menus, it seems impossible to remap the shortcuts—unless the app itself offers that feature, which Excel did in prior versions.
The good news is that it is possible to remap any keyboard shortcut in any app, as long as you're willing to add one more program to the mix: Some sort of macro app. My example uses Keyboard Maestro, but any app that can send a key sequence in response to another key sequence will do the trick.