What version of CCW are you using (or were you using)?
I have version 12 developer edition installed and I don't remember ever being allowed to have more than one controller in the project (as well as one HMI in the project). Perhaps older versions did allow this? I started using it at version 8.0, and I know that it limited the number of PLCs and HMIs back then. Thus, I wonder if you recently updated your software and now are running into this issue.
I know that the PLC tag database link that can be opened within the HMI tag database in CCW references only the PLC in the project. So, in my case, I would only be able to access one PLC's tags.
Now, you can set more processors to communicate within the HMI's configuration page (PLC-1, PLC-2, etc. that you mentioned). You wont be able to directly grab the additional PLC tags in the HMI's tag database editor. However, you can add tags manually.
Think of the database editor as an Excel sheet. You can copy and paste rows at will. Every time you paste, it doesn't overwrite the existing row. Instead, it appends the new row to the end of the sheet. This is true for both the PLC tag database editor and the HMI tag database editor.
So, you can actually make two projects for your application. Both could contain the same HMI application, but each would have different PLCs (I assume each processor has different code and tags). You could also have two projects that have the two PLCs in them, but only one has the HMI in it (to make your life a little easier).
You could then copy all of the PLC tags and HMI tags to an Excel workbook. I would recommend separating each device's tags into separate sheets. Then, you can add and modify the final HMI tags by using the format already generated by the tag database editor on your Excel sheet. Make sure to update the PLC reference to PLC-1 and PLC-2, as appropriate. Also make sure to match tag data types and other characteristics so that you don;t run into any problems (such as matching BOOL to BOOL, INT to INT, etc.). When you are done, you can copy everything to the HMI tag database.
Now, be forewarned that there are some considerations to remember before doing this. If you simply copy everything into the HMI tag database, you may end up with duplicate tags. If you delete tags from the HMI tag database, you may end up with buttons/indicators/entries, etc. that now have lost their tag references. So the order in which you do this matters. There is also an option in CCW to NOT allow tag updates to take effect project-wide, so you could avoid accidentally orphaning a button, for example, by simply deleting a tag from the database. I will admit that I never tested that option, so I cannot accurately describe to you what it will do.
If you were to try this, I would recommend saving you project and making a test project to mess around with to get a feel for how to perform my suggestions, as there a little nuances that are beyond the scope of my post.
I have been doing it like this for years, and I have suffered bumps and bruises along the way, but when you get the hang of it, it isn't so bad. Now, is it as easy as the method you had described? No, but I have never found a way to enjoy the same benefit you had (multiple PLCs that were able to be directly referenced), so unless I have missed an option somewhere to allow it, I can definitely say that the Excel method can save you a lot of manual labor.
