So yes, the Porta Time is not Midi assignable when you right click on it inside ANA 2 UI and also not assignable to ANA 2 Macros via the the Mod Matrix.
A possible workaround could be to try to enable mapping inside Live’s device for the Porta Time and other parameter(s) you’d like to control with the same knob, then create a Group and assign those Parameters to 1 Group Macro inside Live. From there yo should be able to assign those parameters to a Midi Controller or use automation for several parameters.
I’ve sent you an email with a video showing this
Not sure about a simpler/better way to do this TBH, but the Porta Time is not directly assignable inside ANA 2.