So it appears there is no (built-in) option in FCPX to make separate keyboard short-cuts for separate Effects. Even inside the "Command Editor" mentioned by German Dude, you only have ONE shortcut for applying effects, which is for applying the current Default Effect. But you cannot bind multiple, different effects to different keyboard shortcuts. 😢
However... I did find another solution to help keep my fingers on the keyboard. It's not the exact solution I was looking for, but it's the closest thing!
Effect Presets ---> https://support.apple.com/guide/final-cut-pro/save-video-effects-presets-ver462c2078f/10.4.7/mac/10.14
If you make one preset for each built-in Effect that you use often, you can save them all under one new Category (call it something like "My Favorite Effects") and then in the Effects browser, they will all appear together in one spot. You won't have to keep clicking around, typing search text, and scrolling in the Effects browser anymore... because they will all be in one spot!
Additional Note: This solution is superior to the concept of making duplicates of your favorite effects (the actual Motion projects) and putting them into a "Favorites" folder... because if you use Effect Presets then you are simply referencing the original Effect object. Imagine in the future that the owner of the Effect decides to update it with improvements/bug fixes.... if you have saved a copy of the ENTIRE Effect object, then you won't benefit from the updates. However, by using Effect Presets, everything is fine since you are only making a reference to the effect.