Thank you for reporting the issue with FEniCS and how you resolve it.
tkdiff wrote
1. When the fenics solver is complete and returns control back to featools, the last line is "Deleting Fenics data and log files". Depending on the solver variables, like total time, that I set, sometimes the command log window puts a blue bar over that line and sits there for 5-20 seconds, evidently executing the file cleanup, before it allows any further activity in the featool app, ie, it hangs it for that amount of time. Is this normal?
A significant delay during cleanup is not be typical, but could technically occur if you have a lot of or particularly large files (time-steps) to be cleaned up. Or it could potentially be a file system issue with locking/releasing permissions.
tkdiff wrote
2. With my diffusion problem, to get a converged solution using the internal solver, I had to scale the numbers by using the base 10 log of them, ie, log10(c). However, fenics did not recognize either log10 or log. Does fenics only respond to numbers, not equations, for constants or equations?
I believe FEniCS should technically be able to handle most mathematical expressions (as "log" should be converted to "ln" by FEATool). For
log10 a web search gives me this link to this older post
https://fenicsproject.org/qa/10021/solving-expression-with-log10 which does not seem so clear. I would suggest you maybe try to get in touch with the
developers of/support for FEniCS to clarify what is supported and what to do. When you know the correcy syntax you should be able to simply edit the translated "featool-fenics.py" script in the "FEniCS" dialog box.