MBA 13 2017 High Sierra. External LaCie 1TB SSD Time machine added, partition grayed out After loading TimeMachine I decided to partition the SSD; via Disk Utility the partition button is grayed out. I erased the SSD to start again but partition button remained grayed out.
How do I partition the SSD now?
The Disk Utility application can partition the external drive, if you use GUID Partition Map scheme. Also, you need to create a one or more temporary Mac OS Extended (Journaled) partitions in order keep the partition button from being grayed out.

Below is an example of how to create two MS-DOS (FAT) partitions using a 16 GB flash drive.


Erase the drive.


Partition the drive.


Erase the first partition.




The results are shown below.