I'd create a file with particular name or update it if such file exists already. Unfortunatelly I haven't found any way to check whether file exists or not, nor create it with ovewrite flag set to true.
My flow stops in case someone renames a file and it cannot be found, an "on error resume next" block could also work for me in order to ignore this...
Found a way for "on error resume next", if you set "configure run after" to run after failure, but unfortunately the workflow is then being reported as "failed"