One thing another user here made me aware of a few days ago, that might qualify as an anarchistic form of organization that existed within an ML state for at least some time, would be the Artels in Russia.

From the wiki:

An artel (Russian: арте́ль) was any of various cooperative associations that existed in the Russian Empire and the Soviet Union. They began centuries ago but were especially prevalent from the time of the emancipation of the Russian serfs (1861) through the 1950s. In the later Soviet period (1960s–1980s), the term was mostly phased out with the complete monopolization of the Soviet economy by the state.
Artels were semiformal associations for craft, artisan, and light industrial enterprises. Often artel members worked far from home and lived as a commune. Payment for a completed job was distributed according to verbal agreements, quite often in equal shares.[1] Often artels were for seasonal industry; fishing, hunting, harvesting of crops, logging, and gathering of wild plants, berries, and mushrooms were prime examples of activities that were in many cases seasonal (although not invariably).

Additionally I found this stackexchange discussion off them which has some interesting numbers(don't know if they really check out or not):

Overall by the beginning of 1950s there were 114000 artels with about 2 million employees. They made up to 6% of GDP, including 40% of all furniture, 70% of metallic tableware, more than a third of knitted wear and hosiery, nearly all toys.
Artels owned about a hundred of R&D bureaus, 22 testing labs and two research institutes.
Artels pioneered production of the Soviet lamp-based radio receivers and CRT televisions.
During the war artels produced weapons and ammunition such as Sudayev machineguns and artillery shells.

Otherwise I'm drawing a blank too at the moment.

It's more complex. A lot of anarchists joined Communist Party and collectivization was basically inspired by anarchist agrarian communes.