For continuous-time moving RMS and mean, I have a symbol you can download. Qspice/Symbols-KSKelvin/probes and measure/Measure-RMS-MEAN.qsym · KSKelvin-Github/Qspice
A related discussion post refers to
Behavioral True RMS to DC Converter - QSPICE - Qorvo Tech Forum
Here is an example of the performance of this symbol.
example2.Measure-RMS-MEAN.qsch (4.7 KB)
