“Multisite Language Switcher” is very attractive plugin.
However, It may not be available for your site plan.
“Multisite Language Switcher” cannot tell the difference between site A, site B and site C.
Therefore you cannot connect the language when there are site A, site B, site C.
“MSLS Grouping” adds “group_key” to settings of “Multisite Language Switcher”.
For example, you set “group_key” with “SiteA” or “SiteB” or “SiteC”.
You can limit a language site in a group by doing this plugin.
You can display only the first site when there are multiple same language sites in a group.
And, it provide shortcode “SameLangSites” and widget “SameLangSites”.
You can output the list of different groups of the same language.
For example, “SameLangSites” of “site A (English)” lists ” site B (English)” and “site C (English)”.
And, it provide “Language” column on the Table of Sites in network.
And, it provide “Language Flag” in Admin-Bar.