What version are you on? As per the release notes, QM2017 v4.4.0+, "Quicken will now merge dividend and buy transactions into a single reinvested dividend transaction which matches the behavior in Quicken Windows."(If you find this reply helpful, please be sure to click "Like", so others will know, thanks.)
Yes, in QM it is strictly manual. There is no downside I'm aware of to re-doing the transactions as you describe, other than the time it takes. There is also no downside to just leaving as is other than the slight increase of size of the database and transaction list.I don't believe this has any impact on basis and gain reporting, although other may have different experience.