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No, I couldn't find a way to overlay arrows. The only idea I can think of is to put text above and below the arrow, the text can be made to look like a pipe by using underline or strikeout, or custom sprites. But it's rather fiddly (it is hard to get the top and bottom equal lengths/offsets, and sometimes the red arrow disappears (eg if you put G below E)). But maybe you'll get some ideas.(Click diagram for Source)
Hello A. and M.,
Here is another workaround, using queue component, (but not nested arrow...):
@startuml queue TLS { queue WSS { queue API } } [a] -> API API -> [b] @enduml
If that can help,Regards,Th.