Why is my shotcut lagging...?

[ejmillan]

You did not enable proxy for some reason?

Perhaps combining the proxy feature with preview scaling will improve preview performance.
Either way, W10 sometimes has background processes (updates and other services) that can have an influence.

Proxy Editing

Introduction Proxy editing is the process of creating and using low resolution videos and images in places of the original or optimized (Convert to Edit-friendly) files. This provides the advantage that your computer has less work to do in realtime while editing: decoding, scaling, and effects. This is, quite simply, because there are less pixels to compute. Then, when you are ready to export, it will use the original (or optimized) files for full quality. Performance is optimal when the pre…