How to breed specialist pops instead of worker pops and how to manage overpopulation on my capital?

Solution 1:

It would be helpful if you post a couple of screenshots of the planer with issues. It depends on pop type and their citizen rights. Examples why you don't have specialists:

  • Simple robots can't be specialists
  • Droids can't be researchers and rulers
  • Most slaves can't be specialists (you need Indentured servants slavery type to counter that)
  • Some traits like Proles prevents stupid species from complex jobs
  • Are you sure you have enabled those work places and reset priorities?

Most pops can perform any type of job, there is not special specialist pops type. Make sure you actually have specialist work slots first, after that any regular worker with soon promote to specialist

Regarding waiting for next building slot, that sounds strange. Even the tiniest planets can support 50-60 pops. Are you sure you've cleared tile blockers and built enough generator/mineral/agriculture districts? Try replacing building with low worker count (refineries, monuments, clinics) with buildings with high worker count - commercial hubs, high-tier factories, labs and forges.