How many bus lines can a Convimar two module control panel (20510-16950-14510) manage?

It can manage only 1 line, which has an address that you assign via the control unit during the initial setup, and with all the devices configured in the control unit. The address given to the control unit are determined by the architecture of the KNX BUS systems, and for the Convimar control unit specifically, you can select a value for Area between 0 and 3, and Line between 0 and 15. If the BUS line of a control unit is interfaced with another 1 or 2 lines from two other Convimar control units, the three control units must have different Area/Line addresses (e.g., Area1/Line0, Area1/Line2 and Area2/Line0).