I'm not vivid user on Chrome, but probably such thing as "profile" exist here as well (as in Firefox). In Firefox, one can create several profiles, and these profiles can have different settings. So, you can use one profile for everyday, and the other one for Flash.
This seems a bit overkill. Seriously, nobody has that 1 site and uses flash player and always has to grant permissions when he starts / restarts browser?
Allowing flash on all sites it's not safe.
Having multiple profiles is not an option for me.
All of the major browsers are in the final stages of removing support for Flash. Having to explicitly authorize Flash upon each visit is hardcoded into the browser and cannot be bypassed. As Adobe will cease all Flash support at the end of 2020 you can expect the final browser releases for that year to remove support entirely as well. And good riddance to it.