How can I insert logic units by their part numbers while drawing block diagram.

The schematic entry is still supporting the maxplus2 library of TTL devices, so if you are imaging an existing digital logic part, it may be there.

You got already some comments on the programmable analog chip topic. Latticesemi e. g. had a family of pac devices for a couple of years. For some reason, they're vanished now and Lattice is using the technology for dedicated applications only. Cypress is still in the game. Personally, I sometimes considered such a solution, but it never fit.

As another point, some CAD tools are offering an integrated design of programmable logic and all other components. Altium Designer is among the products with yet subsonic pricing. But to my opinion, logic design with Quartus is much more convenient.