There are multiwallets indeed (eg Jaxx) but its not recommended to use them.
For ethereum I use myetherwallet and for my other altcoins I have a different wallet for each and store the passwords/phrases on paper in different locations. I also have backups of my wallets on multiple devices.
A storage manager like the nano ledger looks really good and safe but is a little expensive imo, you can get the same security if you know what you're doing with different wallets.
I suggest you read in about the different wallets for the different coins and make sure you take all the safety precautions that are listed.
Github I don't really use so I don't know much about their value.
Be careful with jaxx, a vulnerability in the Jaxx wallet lead to about $400,000 funds being hacked. Basically, users should refrain from storing substantial amounts of cryptocurrency in these type of wallets.