OS 10.14.6

I have Mojave on my computer. I would like to install OS 10.15 on an external HD. The reason is because if I don't like it, I can just erase it.

Can this be done, if so, how?

jaybass


OS 13.6.4 iMac (Retina 5K, 27", 2017, 3.4 GHz Intel Core i5, 24 GB RAM, 2400 MHz DDR4. SuperDuper. 1 TB Lacie HD