Hidden elements are evaluated & transformed by the plugin just like viewable elements. These elements don't impact what's displayed but do require processing resources. Removing will reduce export time without impacting final result, particularly if large number are present in design.
🔍 How to identify
Unfold all layers in layer panel by holding down the Alt/Opt key and clicking the small "expand" triangle icon to the left of each top-level frame.
Hidden elements will be greyed-out with a closed eye icon to the right of the layer name, and will have a dark blue on the canvas when selected.
✅ How to fix
Manually remove one-by-one or use a plugin to remove all at once.
Manual approach
Select the hidden layer in the layer panel & press delete key.
Plugin approach
There are several free community plugins that automate removal process: