It sounds like the copy-paste tool in the graphical user interface for SimBiology could help in your case. To open the SimBiology app, type simbiology in the Matlab command line and hit enter. In the app you can add the two models A and B. Then you can rubber-band select all model components in model B that should be copied into the destination model A. To copy the selection click on Copy in the right-click context menu.
Then switch to model A in the BROWSER panel on the left, under the Project tab.
Paste the copied model components from model B into model A by right-clicking on the diagram and selecting Paste.
These screenshots are taken from the latest version of SimBiology, Matlab R2020b. There you can customize the copy behavior ("Copy Options...", the third entry in the context menu for copying model components). This can be helpful if you want to copy more complex models, for example when the two models contain species with the same name, or also for copying rules, events, or observables.
After having copied model B into model A, you can connect the two models by adding a rule, or a reaction, between the corresponding species/parameters.
I hope this helps.