In <ROM>, you can directly configure auto-use and usage delay for efficient battle. You can enable auto-use of skills without registering them in the shortcut bar by following the steps below:

[Changing Skill Usage Method]

Tap the menu icon in the top right corner, then go to [Skills].
Toggle the A button to turn ON/OFF auto-use of skills.
Press the clock icon next to the skill to adjust how often it will be used in seconds.