When creating entries in a list, you have several options to customize the New Item form.
Control which fields can be updated via the form and the order in which they appear by:
Refresh your page and click on +New. The form should be updated with the new column(s).
You can choose to show or hide certain fields based on conditions (for example, only show Field B when Field A is populated). Follow the steps above, but select 'Edit conditional formula' to enter the condition. You need to do this on field which should be displayed or hidden, not on the field that is conditional. In the example cited, you would apply the formula on Field B, even though Field A triggers the logic.
Conditions are written in a specific syntax. For details see Microsoft Documentation: https://docs.microsoft.com/en-us/sharepoint/dev/declarative-customization/list-form-conditional-show-hide#specify-conditional-formula-to-show-or-hide-columns
Advanced formatting requires PowerApps (licensed separately) but there are some simple out of the box options available. You can add headers and footers for example, or create sections with headers.
This formatting requires JSON. You may need to Google to find examples of "list form json formatting" or contact EASI SharePoint Support.