as long as the permissions of the folder are not locking down the visibility then it should be visible in the portal. 

that's correct, but I meant the category.

I.E.: The category will be assigned to Workspace A. If the requester want to raise a ticket and is selecting workspace B, the solutions will not be shown in the related solution section.

Sorry, I’m confused, in the portal where the requestor lives, there is no seperation with Workspaces, until you are raising a ticket. So it should show you the most relevant article in the “incident” form regardless of the workspace. 

or I may be misunderstanding your usecase. 

I guess you do, of I am missing something . I will try to explain;

When the requester is raising a ticket, the first field is to select the workspace the ticket is related to.

The second field is the subject.

Logically the requester is first selecting the workspace because it is the first field (and cannot be changed as far as I know). The when workspace A is selected and the subject is entered...there will be no items KB-categories shown of workspace B.

I hope this clarifies things.

Thanks for your help anyway, I hope you have a solution of magic tip.

Ah, you can hide that field, in the field manager, you can opt to not show this to the requestor and that will hide the field and help with your problem! :D 

That will help to solve this specific issue (thnx!), but creates another issue. The business ruling of the workspace-categories doesn't work than. 

Offcourse I can create another field to simulate the workspace field to solve that as well, but that is more like a workaround instead of a stable functionality/fix.

Yeah, it’s not perfect, but also it might give you more flexibility on catagorisation of the tickets.