Database
[{"_id":"12345","1List":[{"Comment":"TEßT Comment","TEXT_VALUE":"Another test string","REASON":"No Reason"},{"Comment":"TEßT Comment the second","TEXT_VALUE":"Another second string","REASON":"No Reason again"},{"Comment":"no changes","TEXT_VALUE":"Another second string","REASON":"No Reason again"}]},{"_id":"12346","1List":[{"Comment":"TEßT Comment","TEXT_VALUE":"Another test string","REASON":"No Reason"},{"Comment":"TEßT Comment the second","TEXT_VALUE":"Another second string","REASON":"No Reason again"}]}]
Query
db.collection.update({},{$set:{"1List.$[element].Comment":"TEST Comment"}},{arrayFilters:[{"element.Comment":"TEßT Comment"}],multi:true})