What QU do you have?
You could use the ALT OUT to feed your IEM’s. In the set up menu in the IO settings
go to the surface menu, under the ALT OUT settings select the main LR mixe or if you using mono IEM select the L+R.
Here’s another option…..still using the ALT OUT select the PAFL output option.
That will allow you to hear the main mix and then when you want to go back to your dedicated IEM mix just select PAFL on that mix master.
Doing that you will want to go to the set up menu and under the audio tab, PFL menu
de select the option for the PFL to follow the mix selection, doing that will allow the
PFL to stay selected on your monitor mix when you change layers on the board until you
select another PFL.