Transmutably is a rare word and it can be challenging to come up with synonyms that convey the same meaning. However, some of the potential alternatives for transmutably include mutationally, transformably, convertibly, alchemically, and metamorphically. These words share the common theme of transformation and change, and could be used in many contexts to describe fluidity and adaptability. Other words that could work as synonyms for transmutably include mutagenically, transformatively, and transmigratorily. Regardless of which synonym is chosen, it's important to ensure that the context is clear and the meaning is conveyed accurately.