I’d love the ability to provide pre determined support points for my models instead of manually placing them in “edit” mode. Referring to the two mockup images that I’ve (hopefully) included below, the process would be to select one of the models that you want to load custom support points for. On the edit pop up window, you would then get an additional option to load the support points from a file. If you press that button, you would then get a file selection dialog where you can choose a file with XYZ points of the support points you would like to have. These points would need to be in the same coordinate system as the original STL file that you loaded for that model. Once you do that, you will then see those points on your model. You could then do some further editing if you wish, confirm the model looks good, etc, the press Apply as usual.
You probably already know this, but just in case: once you’ve designated the supports once, you can right-click the model and import an updated STL while maintaining the previous support points. Doesn’t work for completely new parts, but if you’re iterating it can save you a ton of time.
I’ve also done models before where I created my entire own support lattice in software outside Preform, and brought the whole thing in as an STL.