How to add CSS style to Forge UI kit components

[ibuchanan]

@Holger,

Over on another thread, @ImranParvez answered:

How to create Form with side by side input fields

Hello @AzharPathan welcome to atlassian developer community. When you use UI kit, it uses the atlassian design guidelines and in it we do not have side by side text fields. You can use custom UI instead to achieve the desired state. Thank you!

It looks like Forge Custom UI is your only option.