How to enable non webstore extensions in google chrome

For Win7/8/8.1 and 10:

1) download Chrome group policy templates 

3) Copy [zip]\windows\admx[yourlanguage]\chrome.adml to c:\windows\policydefinitions[yourlanguage]\chrome.adml (not c:\windows[Your Language])

4) In Chrome, go to Settings -> Extensions

5) Check the Developer Mode checkbox at the top {Shown in the picture below}

6) Scroll down the list of disabled extensions and note the ID's of the extensions you want to enable. LogMeIn, for example, is ID: nmgnihglilniboicepgjclfiageofdfj   {shown in the above picture}

7) Click Start -> Run, and type gpedit.msc and hit Enter key

8) Expand User Configuration -> Administrative Templates -> Google -> Google Chrome -> Extensions

9) Double-click on "Configure extension installation whitelist"

10) Select "Enabled", then click "Show..."

11) In the list, enter all the ID's of the extensions you noted in Step 6

12) Click OK and restart Chrome.

Even though the 'Enable' box LOOKED grayed, it allowed you to check it.

sauce: https://productforums.google.com/d/msg/chrome/9NlMAr6uEVc/ambkrcKpi1cJ