Flatten Selection to Bitmap 
A Figma plugin to rasterize layers at a high resolution
asset bitmap export flatten image images resolution
Commands
Flatten Selection to Bitmap
Rasterize the selected layers at a high resolution (2x, 3x, 4x, 8x, or 10x). (This is to work around a limitation in Figma where layers can only be rasterized at 1x resolution.)
If layers in the selection contain strokes or effects that extend beyond the layers’ bounding box, the position of the resulting image layer may be different from that of the original layers.
Settings
Set the resolution at which layers are to be rasterized.