I’ve made some progress on the display settings issue. The Samsung display has built in Eco and Off Time Plus settings to conserve power. Yesterday I turned both of these off, hence the control of turning the display off should now be the sole responsibility of the MacBook Pro.
This morning, for the first time, the settings have been retained overnight. However, the widescreen resolution has been set to ‘Default for display’, but is is the 2560 x 1080, which I was using and the 3440 x 1440 was missing from within the ‘Scaled’ list.
A restart has resulted in the original problem. All Display settings have been lost and all have to be changed to my preference again, with the 3440 x 1440 resolution available again.
It still looks like Apple have work to do.