I've found that in order to build up my research or wealth planets I will often set the sliders to half manu and the other half res/wealth (or something like this). Once built up I will then go back and reset the sliders to 100% res/wealth. This gets really tedious when I unlock a new building (farm, moral or res/wealth), and have to cycle through all my colonies and reset things to 50/50, just to set them back to 100% a few turns later.

What I propose is that unspent manufacturing production (so no other buildings in list, and no shipyard/off shipyard) goes towards res/wealth, depending on how the sliders are set. This way, I could leave my res/wealth planets to 50/50, or even 99/1, and not have to go through every colony and micromanage the sliders every turn.