I am not sure what do you mean "connect". You can use script to modify their relative positions:
similarly for yz.
You can also add them into a structure group: https://optics.ansys.com/hc/en-us/articles/360034382434-Structure-Groups-Simulation-object
Symmetry can only be performed with boundary conditions. When the device AND the source polarization have symmetry, you can apply symmetry BCs. Using
?getnamed("FDTD","x min bc"); to get the current x min BC. you can set it:
setnamed("FDTD","x min bc","symmetric"); for symmetric BC
setnamed("FDTD","x min bc","anti-symmetric"); for antisymmetric BC
Other direction is similar.
Please refer Symmetric and anti-symmetric BCs in FDTD and MODE