How to customize forms in a new application

How to customize forms in a new application

Do you mean, to save your customizations within the new application?

In general have a look at the doc: Customize Form

Also have a look into the following thread to understand, when to use fixtures and exporting customizations: Export Customizations vs Fixtures - #6 by bghayad

If I customize the form, my other ERPNext is similarly or similarly customized.What should I do?

I know that in a production environment it is possible to back up the database and restore it

In a development environment.I can create a new application to customize but I don’t know how

For example, change the number of columns, width, and layout of the form