Dependant visa extension - simultaneous online application?

Dear all,

and yet another question - can actually a dependant apply for the visa extension at the same time with the main applicant, using this online form https://visas-immigration.service.gov.u ... nt-partner? I noticed that for the separate paper applications the address of Home office is written slightly different for dependants than for the main applicants (same address but different departments), while I read that the documents of the main applicant and dependants must be sent in the same envelope...

Thanks a lot!

Iakov