Currently for SRT outputs there is a red indicator at top of the GUI that turns yellow if there's any problem or issue with transmission from Vmix.
I would love an indicator within the SRT input window (or otherwise) that shows when an SRT input is lost or unstable.
On a related note losing an SRT input feed requires a reset on the unit to reconnect. Or it may also require a full delete and recreation of the input to reconnect.