Yes, you want to use gears and cadence when in Slope mode.
There isn’t an indication when a slope mode interval is up next (like there is with the Android app). However, the Session Player alerts you to upcoming Slope Mode % on the power chart.
Have you tried using the Session Player yet on a laptop/tablet/PC while running the phone app?
If you review the workout ahead of time MIXEDMODE will appear in the description or a #MIXEDMODE tag at the bottom.
During the workout you’ll see a label below the target watts such as –
XXX (watts)
Target: Slope 5%
The label will also indicate when the interval is SMART such as XSSR based.
Same labels appear on the Session Player above the rainbow gauge.
You’ll need to practice a bit with MIXEDMODE workouts to determine which gears work best with your trainer.
The slope mode intervals in the workout you did are all-out sprints so there really isn’t a target limit. Go as hard as you possibly can at a high cadence.
MIXEDMODE also ensures no spiral of death (ERG mode lockup) when transitioning to high watt intervals.
Related –
New SMART Workout(s) - General - Xert Community Forum (xertonline.com)
Lots of newbie tips in this thread –
Beginner questions - Support - Xert Community Forum (xertonline.com)
Welcome aboard. 