Copying a Module
You can copy an oscillator or filter (with or without modulations) and paste it to another (similar) module. This works when copying and pasting modules in the same preset, as well as when you want to copy and paste between presets.
For example, consider the case where you configure an oscillator module with specific wavetable, unison, detune, and warp settings. In addition, you have LFO 1 modulating the wavetable position (WT POS knob).
Right-clicking the oscillator label and choosing Copy in the menu copies the module to Serum’s internal clipboard. Right-clicking another oscillator module and choosing Paste in the menu pastes the configuration (all settings except the WT POS modulation) to the corresponding module.
To copy and paste a module configuration including modulations, right-click the oscillator label and choose Copy (w/mods) in the menu. Pasting to a new module now includes the WT POS modulation from the earlier example.
As mentioned, this copy and paste operation works even after changing or initializing a preset. In addition, the module configuration stays on Serum’s internal clipboard after pasting, allowing you to quickly paste the same configuration to multiple modules as needed. It is not possible, however, to copy a module from one instance of Serum to another.

Hold the Option/Alt key and drag the module label (next to the power button) to another (similar) module to copy the module without modulations.
Hold the Shift-Option or Shift-Alt keys and drag the module label to another module to copy with modulations.
Dragging from one module label to another without any keyboard modifiers swaps the two modules (including modulation assignments).