I am sorry, I have another question (then, I am hoping not to bother you again for a while 
). What I would like to do is change a block of the operator a third time, and recompute the block-LU factorization for that block. According to -options_left, it seems that the change in option is detected, the options at the first set(Sblock, sparams="..."); persist. I also tried to change the options of the independently (set(A11,...);. in Sblock = [[A00, 0], [0, A11]]). Could you please take a look, what am I missing?
ChangeOperator-MWE2.edp (2.3 KB)