Why should plugin developer bother? who is still working from a desktop? (and how am I supposed to test it? should I buy a 21 inch just for that?)

(Just bought a 15'' laptop for my mother. I don't expect her to use it more then she used the desktop, but less wires and easier to move to clean below it)

just another example of "(stupid) decisions, not options". Even with your screenshot it is obvious the customizer can be easily wider... this should just be an option, or at least expose and API for it.

In addition being wider is not enough unless the customizer can take advantage of the additional width and show more information, for example show two columns of sections instead of one. Right now all this change does is probably adding white space.