Firmware 6.20 lacks the ability to add Strength Training to Blocks in the MultiSport activity. I ask Garmin representatives to add it in the next firmware.
The ability to transition from Strength training activity to the next activity, for example, Running, is also sorely lacking.
Now it works through Settings - Resume later and Change sport. For example, after running, you need to do Strength training, and then finish your Running class again.