You can break an activated chain mode in sxhkd by sending it SIGALRM.
Additionally, you can change the way of normally exiting a mode by the commandline argument -a.
Finally, you can set 'double-mode' keychains, e.g. alt + m : alt + m which will only listen for alt + m when already in the same mode and then invoke the respective command.

Taking all together, it becomes possible to create chained modes which can be exited by pressing the same combination of keys twice (or any other key combination) instead of the pre-set escape,
which often interferes with actual program operation for me.

This could provide the last building block for my mode-based desktop version built with sxhkd and polybar.