Well, "manager" might be stretching it a bit. The idea is not having to manually look up and install updates when using a Chromium-like browser that doesn't use the WebStore plugin to handle these things. This is done by employing this method which uses JSON preference files to point to local extension packages.
If you're on ArchLinux, you can install maninex via the Arch User Repository. Use your favorite AUR helper or simply git:
git clone https://aur.archlinux.org/maninex.git cd maninex makepkg -sri
On other distros you can use pip to install maninex and handle dependencies (one: requests).
pip install maninex
Maninex won't run on Python versions lower than 3.5.
usage: maninex [option]
options:
-h, --help show this help message and exit
-c, --clean clean up (i.e. remove) backed up extension files
-i, --install install all extensions that aren't already installed
-l, --list list all extensions and their current status
-p, --print-skel print the contents of a skeleton config file to stdout
-r, --remove remove all extensions that are installed but not in the
config file
-s, --scan scan for installed extensions not in the config file and
add them to the config file
-u, --update update all extensions
set up paths and extensions in maninex.conf
Maninex depends on a configuration file named "maninex.conf" for which
it will look in three places: First in $XDG_CONFIG_HOME, then in
$HOME/.config and finally in the same directory that the script is in.
maninex --print-skel prints out a base config file with some basic
instructions. Therefore, to get started you can run
maninex --print-skel > ~/.config/maninex.conf.
Edit maninex.conf and add extensions by their ids under the [extension]
header. You can use the scan option to add extensions you manually
installed before (see below). To find out an extension's id, search for
the it on the Chrome
WebStore.
The final part of the extension page's URL is the id. For example,
this
is the url of uBlock Origin and its id is therefore
"cjpalhdlnbpafiamejdnhcphjbkeiagm". Every extension id should occupy one
line under the [extension] header. Optionally you can prepend an
identifier for the extension like this:
uBlock Origin = cjpalhdlnbpafiamejdnhcphjbkeiagm
This is recommended as it will make messages more descriptive, for
example Extension "cjpalhdlnb…" installed. will become
Extension "uBlock Origin" installed.
Run maninex -i to install all the extensions in the config file. Run
maninex -u to look up and download updates.
This will remove old extension files that were backed up during previous updates.
List all extensions in the config file and whether or not they are installed already.
Scan the extension directory and add all extensions to the config file that aren't included already.
The opposite of scan. Remove all extensions that aren't included in the config file.