Use value to secondary playbook

You may be able to use custom lists to accomplish this. You can save the variable with the category as PlaybookA-Variable-[Case.ID] and save the variable as the identifier list using the "Add String to CustomList" action and then use the "Is String in Custom List" in the PlaybookA-Variable-[Case.ID] Custom List (or something like that). I do something similar to this for noise reduction to tune out duplicate alerts. At a very high level it works something like this:

Custom lists are an option -- I'm increasingly using the Tools → Set Context Value action to set variables with an Alert, Case, or Global scope. For example, once you set a Case variable you can reference it with [Case.KeyName] . Global is new...and looking now I don't know how to reference it directly but I expect using the results of Tools → Get Get Context Value would work just fine.

oooooh! i want to look into that further!

Thanks to you, I'll try both and even you guys give me another idea to try it.

But basically that I want is set and get a value in a playbook (with the functions Set Context Value and Get Context Value), attach a seconday playbook (with the function Attach Playbook to Alert) and then, in this new playbook, call to this last value declarated/set in the behind playbook.

Sounds like a perfect use case for Set Context Value using the Case scope. Set the variable in first playbook and reference it in the second using the [Case.xxx] notation

The use of Context Scope should be marked as the solution. Nicely done!