This is how to enable the Violentmonkey extension in Chrome Web Store guide.
It is similar to what I have explained in how to enable back uBlock Origin extension in Chrome Web Store.
Now the "Add to Chrome" button is grayed-out and it cannot be clicked.
The remark says: This extension is no longer available because it doesn't follow best practices for Chrome extensions.
But with a simple hack, you can get back the "Add to Chrome" button to blue color.
Then you can click on it, to install this open source user script manager extension.
How to enable back Violentmonkey in Chrome Web Store
Now go to Violentmonkey extension page at the Chrome Web Store.
Right-click on the gray color "Add to Chrome" button.
A menu pops up, click "Inspect".
You can see this line of code highlighted in light blue color.
<div class="VfPpkd-dgl2Hf-ppHlrf-sM5MNb" data-is-touch-wrapper="true">...</div> Click on the three dots.
A new row of code appears below it.
Drag the bottom scrollbar, until you see the word: disabled in the code line.
Change the word disabled to enabled.
To do it, double click on the word disabled, and a blue color background appears.
Type the word enabled onto it, and automatically it would be replaced.
Press the "Enter" key, instantly the gray colored "Add to Chrome" button changes to blue color.
Click the X symbol to close the Inspect Element page.
Now click the blue color "Add to Chrome" button to install the browser extension.
This is how to enable back the Violentmonkey Chrome extension.