Using Linkers In Bb3?

Hello,
I can't seem to figure out how to use linkers in BB3. I see them in the template but I cannot figure out how to create more. This seems like a really useful feature. Any ideas?

 

Select the item you want, hold control and select the other item you’re trying to link to. Bottom left you will see a + and an x symbol. Click the + and Select “Link Selected”. Done.

 

Thank you so much @AppNasty