The free to use, open source toolkit YAKINDU Statechart Tools (SCT) provides an integrated modeling environment for the specification and development of reactive, event-driven systems based on the concept of statecharts.
Take a look at the editing features of the YAKINDU Statechart Tools in this video.
Learn in these screencasts:
how to integrate your C code with state machine models,
how to use breakpoints for debugging purposes and
how to store execution states of simulations as snapshots.