Can LTSpice waveforms be exported for further processing?
Right click on the plot and then export data as text.
You can then pick which nodes you want to export and the file name

If you want to export V(noise+sig) then create a b-source with
V=V(noise+sig)


then record the output of the b-source node in the file  (you could even label the output node as Vnoiseandsig, so you know what it is in the file)
Another useful thing to know is that you can export data and then reimport it in a PWL file, which is useful for comparing simulations if the comparison can't be done in any other manner:
https://www.analog.com/en/technical-articles/ltspice-importing-exporting-pwl-data.html