TL;DR - How does one create a complex User Interface in Photoshop in a way that Photoshop doesn't slow down to a crawl?
I create a lot of complex User Interface scenarios with Photoshop and routinely get to 10-20 layer comps and hundreds (thousands) of layers.
Layer Comp 1 has a list of items with checkboxes. There is a filter across the top (Aging Accounts that are less than 30 days old, more than 30 but less than 60 ...). There are drop-downs which lets users add x to y; merge x; delete x; and icons which display different information depending upon the above mentioned filter.
Layer Comp 2 has a drill-down (user selected on one of the items and gets a sub-item and a new set of checkboxes are displayed.
Layer Comp 3. User selects drill-down line (checkbox selected) and goes to drop-down. (Drop-down revealed and selection highlighted)
Layer Comp 4: Pop-up is displayed allowing user to ....
By the time you go through several scenarios you have dozens of comps; and dozens of variations.
I use smart objects as much as possible; and organize, group, and label my layers meticulously so finding items is simple. However Photoshop is slowing down tremendously.
My, not so good, solution is to create as many different .psds as is logical. But sometimes (too often) it makes "logical","organizational" sense to keep things in one file.
I hesitate flattening layer groups as I update them often as the requirements change (or more accurately stated they become more and more precise).
What is the best solution to this problem (so many layers that Photoshop slows down)?