Are there other, prehaps even better software options with this functionality? For me these are currently just learning tools for curiosity, as I still dive stricly in rec limits. Visualization of tissue nitrogen loading during surface interval would be interesting. With Subsurface I just have to fiddle with starting time of the dive plan to see how much residual nitrogen effect there is.
I don't know if there are other, better software options.
If you want to see the tissue loading graph for the SI, you might just try planning 2 dives in Subsurface and then doing a Merge to combine them into one dive. Then it should show the middle portion of "the dive" as depth of 0 and you can mouse over that portion to look at the tissue graph. I haven't tried this myself, so I'm not SURE it will work, but I expect it would.