Save Effect Preset in Final Cut Pro

Although you cannot change the default parameters when applying templates in Final Cut Pro; custom effects presets can be saved as a way to quickly reuse preferred parameters.

Apply the desired effect to a clip

After customizing the effect parameters in the Video Inspector, in the lower right click "Save Effects Preset"

Title your preset and select which attributes you want to save to the preset

If you regularly use this effect with these parameters, consider setting it as your default effect

Find more details about saved effect presets & default video effects from the Final Cut Pro User Guide.