Maysspayout, SendMany, Bulk Payouts with Bitcoin Core Do I have to download the whole bitcoin blockchain (145GB) to be able to do a sendMany transaction with Bitcoin Core? 

Are there other Desktop Software, where I can do a masspayout? 

Maybe an App, where I can read a CSV like this:

address amount,

address amount,

...
Electrum is an SPV wallet which means you don't need to download the entire blockchain. It will be up and running in a few minutes

It has a handy sendtomany feature where you can even upload a csv file