How to enable disabled extensions?

[testuser3130]

Description of the issue:
Unable to enable the third-party extension, brave disables the extension

**Steps to Reproduce (add as many as necessary):

1. Download the extension https://medium-unlimited.ml/medium-unlimited-1.4.4.crx
2. Go to More Tools -> Extensions and drag the extension

**

Actual Result (gifs and screenshots are welcome!):

Expected result:
Extension to work as expected

Reproduces how often:
Happens every time with this extension

Operating System and Brave Version(See the About Brave page in the main menu):
macOS 10.14.5
brave: 0.65.121

Additional Information:
I looked at the docs, it seems weird that Brave does not allow third-party extensions.

[Mattches]

@testuser3130,
To allow 3rd party extensions, I believe you must first enable Developer mode on the extensions page – you should see this optional toggle in the top-right corner of the page:

[testuser3130]

I already enabled it. I still see the error

[Singingintherain]

I also have this error

macOS 10.15 Beta (19A512f)
brave: 0.66.100 Chromium: 75.0.3770.142 (Official Build) (64-bit)