Hi @ECornus ,
I don’t think there’s a way to style the slide-in form. Have you considered using a pop-up one instead? Due to its styling nature, it’s more prominent.
With the standard slide-in form, a trick you could use is to add a few line breaks. That will naturally make the text take more space and thus the box will increase. Depending on the implementation of this, it might look a bit tacky, so be mindful of the aesthetics of it.
I hope that helps,
Eli