Geometry tool

I have opened up an S3 product and have drawn a geometry on the 1km S8 band. when I go to analysis-histogram and try to find the geometry mask under the ‘use ROI mask’ menu, there is no geometry mask visible. However, if I go to one of the 0.5km bands and do the same thing, the geometry is accessible there. I have opened up the product initially using the third option in the drop down menu where no product resolution is specified.

Yes, this is still due to our multi-size issue. The support for multi-size products like S3 SLSTR is not optimal yet.
If you open 1km product it should work. You can also use the multi-size version (third option) and resample the data to a common resolution.