S1 Multi-temporal stacking

Dear all,
I have a time series stack of S1 image processed and stacked. I would like to know is it possible in snap to keep adding new set of time series data to the same stack if so how to proceed on this?

Also, i have performed following steps below to create the first time series stack. is the process flow right?
Thermal noise removal
border noise removal
orbit correction
filtering(refined lee)
terrain flattening
terrain correction

Thank you in advance

does it work to coregister the stack with the new added image?
The steps seem fine to me, although I would put filtering after flattening