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Viewer Viewer panel consist of one or more viewports organized in grid and toolbar underneath it (only in single-slide mode). Currently selected slide is highlighted with the blue dashed border. When user adds new viewer panel its grid has only 1 column and 1 row, so it's single cell grid. When changing grid size application will always ask what to do with slides that were already loaded into grid - whether application should preserve it or clear all.
Toolbar consists of (left to the right):