You can lower the visual quality of parts in the viewport menu; this will remove details like roughness and mould lines from parts. It means not as much graphics processing is required, so the workshop should be able to perform better on your computer.

Flat Shading with Boundaries is also a viewport setting that requires less power.
Also if you are under windows, make sure that your browser is hardware accelerated (uses GPU instead of CPU). For some reason it is not always set like this by default.

How exactly do I set my Firefox browser to GPU acceleration?

EDIT: Never mind, I figured it out via web search. Thank you!