It is extremely important for big users of MainWP to automate the master>slave process without having to manually add sites.
The filter is useful in some circumstances, however it would be more beneficial if there was a plugin, that could be preconfigured with the master dashboard details etc, once activated automatically connected that child site to the master.
I’m currently using MainWP for 300+ Wordpress Sites, and growing, and I’m not even halfway of manually adding the sites, I’m using Softaculous, and with the use of a preconfigured plugin I could automatically install, and activate that plugin through Soft, and that could automatically connect the child to the master.
@Jonah_Marsden It’s not exactly what you were requesting but this may be at least a little helpful until the MainWP Child Plugin evolves. There is also the Import Sites feature that you may edit with your Child Sites connection details and auto add them to the MainWP Dashboard - if you have not already considered this.
Considering that the MainWP White Label Extension already exists to take care of the MainWP Child Plugin Branding - In order to make this request a lot easier to pull off, I am making my personal MainWP Child Auto Downloader plugin repository PUBLIC. You may set this plugin up and offer it as a “Downloadable” for your services.
You may download and customize it as you would like here: