Edit: I found the documentation for this setting so the below steps can be applied to any OS: According to https://www.chromium.org/administrators/policy-list-3#PluginsAllowedForUrls – you can add sites you want to automatically run flash on with this list. This includes * – but please don’t do that – seriously, see end of this answer.
Detailed Windows Steps:
WARNING: mistakes in your registry could prevent your computer from booting or working correctly – use at your own risk.
You can add sites to your registry for Chrome Policies “PluginsAllowedForUrls” – this is not specific to Flash, but is currently the only setting I see impacted by the change when viewing: chrome://settings/content/siteDetails?site=https%3A%2F%2Fmytrustedsite.com
Using regedit, navigate to the below key & create new String Values for each site you want to permanently allow Flash to run on (http:// could be used too if you just throw all caution to the wind):
[HKEY_LOCAL_MACHINE\Software\Policies\Google\Chrome\PluginsAllowedForUrls] New String Values can be added here for trusted sites: "1" = "https://my.trustedsite.com" <-- specific site format "2" = "https://[*.]trustedsite.com" <-- if you want to trust all sub-domains too "3" = "https://*" <-- please don't do this. seriously, don't do this.
Note: If “Google\Chrome\PluginsAllowedForUrls” Keys (folders) do not already exist, create them, then create the String Values.
Restart Chrome & open your trusted site – Flash should now load & site settings will reflect “Flash allowed by your administrator”
Flash allowed by your administrator
Extra word of caution about enabling this with ‘http://* or https://*’ – PLEASE DON’T DO THIS.
See any # of articles on the security risks of flash, which may stop getting any security patches by Adobe as early 2020. here is a recent USA Today article