you can add a hundred or more inputs and outputs to any channel
usually additional channels are used for sidechain signal. So you have not just a one optional sidechain for a track, but roughly unlimited. Sending an audio onto different from 1\2 input channels, automatically adds 2 more channels to a track and a meter for them. Click routing on a needed track and there's the option in the right top corner (AFAIR), switch it back to 2 channels.
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