How to withdraw pbs dependent application?

I’ve applied using the old link for PBS dependent and want to withdraw it as its asking me to book an appointment and I would like to do it with App if possible.

While going through withdrawal request I am not sure what category I should select to withdraw the application.

Also, should I apply via app again before I withdraw my other application? Current Visa ends in 3-4 days so don’t want to take any chances.

You don't get choose to apply through the app. Ukvi decides that, IF you are eligible.

If you are being asked to book an appointment, you cannot use and are not eligible for the app for biometrics