Registration for children born in the UK whose parents subsequently acquire ILR/PR is an entitlement and can be done from abroad.
However, be aware that applications of British passport from abroad can take between 6 months and a year (see timelines on these forums). If acquisition of British citizenship automatically voids your child's current nationality, s/he may have issues with leaving his current country of residence until s/he acquires a British passport.
maxflip50 wrote:dear friend, as i can see you are newly registered, do not expect any decent advise from here as many do not know what are they talking about (they tell you the problem, not the solution), i am telling you from my experince
Given your rather low opinion of these forums expressed in
another thread, I am somewhat surprised that you continue to post questions over here. I hope that us pointing out the problem leads you to thinking of the solution. We often can't tell you the solution unless you have spelt out your entire circumstances explicitly, which most people don't, just as it is not clear as to whether you have ILR or are hoping to acquire it soon and whether the above is a hypothetical question or a factual one.
I am not a lawyer or immigration advisor. My statements/comments do not constitute legal advice. E&OE. Please do not PM me for advice.