Hi, yes the toIQMPO method was getting difficult to maintain and I wasn't sure if it was necessary to have anymore since the library now includes AutoMPO, which can make many common types of IQMPOs.
We could consider putting toIQMPO back in, but before doing that, what is the use case for which you need it? Perhaps you can accomplish what you are trying to do another way.
I should mention that toIQMPO was only ever reliable for "hand made" MPOs which had entries which were either order 1 or else zero. I would not recommend using it for MPOs which were, say, obtained numerically by summing many smaller MPOs together, as such MPOs could have lots of small entries which were nonetheless important.